WO2010055615A1 - High grade silicon and thermoelectric conversion material - Google Patents

High grade silicon and thermoelectric conversion material Download PDF

Info

Publication number
WO2010055615A1
WO2010055615A1 PCT/JP2009/005569 JP2009005569W WO2010055615A1 WO 2010055615 A1 WO2010055615 A1 WO 2010055615A1 JP 2009005569 W JP2009005569 W JP 2009005569W WO 2010055615 A1 WO2010055615 A1 WO 2010055615A1
Authority
WO
WIPO (PCT)
Prior art keywords
silicon
waste
silicon waste
thermoelectric conversion
conversion material
Prior art date
Application number
PCT/JP2009/005569
Other languages
French (fr)
Japanese (ja)
Inventor
林正裕
大島建司
玄場公規
安野拓也
坂本直道
Original Assignee
株式会社林商会
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 株式会社林商会 filed Critical 株式会社林商会
Priority to JP2010537671A priority Critical patent/JPWO2010055615A1/en
Publication of WO2010055615A1 publication Critical patent/WO2010055615A1/en

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/037—Purification
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/01—Manufacture or treatment
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/80—Constructional details
    • H10N10/85—Thermoelectric active materials
    • H10N10/851—Thermoelectric active materials comprising inorganic compositions
    • H10N10/855—Thermoelectric active materials comprising inorganic compositions comprising compounds containing boron, carbon, oxygen or nitrogen
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to high-purity silicon, and more particularly to high-purity silicon produced by reusing silicon waste generated from the production process of silicon wafers.
  • the present invention also relates to a thermoelectric conversion material, and more particularly to a thermoelectric conversion material produced by reusing silicon waste generated from a production process of a silicon wafer.
  • the silicon single crystal of the semiconductor substrate raw material is manufactured through processes of silica reduction, conversion to monosilane, hydrogen reduction, single crystal silicon pulling process, and consumes a lot of energy. Furthermore, the silicon chip as the semiconductor substrate is silicon The single crystal is obtained by slicing a single crystal as a silicon wafer through wrapping and polishing steps, and finally dicing. The yield from the silicon single crystal to the silicon chip is only 30%, and the remaining 70 % Is treated as waste as silicon sludge.
  • Patent Document 1 in a method for producing silicon for solar cells, silicon waste generated in the semiconductor industry is used as a starting material, and this is first melted, and then has a through-hole at the bottom, and a silicon compound. Filtration is carried out with a filtration device filled with a substance mainly composed of a silicon compound as a filter material in a filtration container composed of the substance as a main component, then subjected to an oxidation treatment after the filtration treatment, and then subjected to a decompression treatment, A method for producing silicon for solar cells, characterized by unidirectional solidification, is disclosed.
  • silicon sludge waste is deposited in a landfill or burned in an incinerator, but if sludge is deposited in a landfill, there is a risk that oil and glycol will leach into the soil, It has become an environmental problem.
  • incineration in an incinerator converts silicon powder in silicon sludge into contaminated silicon dioxide and deposits it in the soil.
  • silicon powder waste is accompanied by environmental pollution, an increase in cost for environmental measures is a problem.
  • the concern about environmental pollution from silicon powder waste is expected to increase further in the future. Therefore, there is a particular need for a method for easily and safely reusing a large amount of silicon sludge waste while reducing environmental measures costs.
  • Patent Document 1 since the invention disclosed in Patent Document 1 must be subjected to a filtration treatment, the filtration treatment requires time and cost, and is not accompanied by profitability as industrial reuse.
  • silicon waste can be reused easily and inexpensively to obtain high-purity silicon, it can greatly contribute to the reuse of silicon sludge in consideration of environmental measures.
  • thermoelectric conversion material from a mixture of silicon and iron using the melting method.
  • the metal formed by the melting method is used.
  • the semiconductor phase ( ⁇ phase) of the Fe—Si-based thermoelectric conversion material can be obtained by further heat-treating the phases ( ⁇ phase, ⁇ phase) for a longer time.
  • the dissolution method requires time and cost, and is not accompanied by profitability as industrial reuse.
  • thermoelectric conversion material if silicon waste can be reused easily and inexpensively to obtain a thermoelectric conversion material, it can greatly contribute to the reuse of silicon sludge in consideration of environmental measures.
  • the present invention has been made to solve the conventional problems, and an object of the present invention is to provide high-purity silicon produced using silicon waste. Moreover, an object of this invention is to provide the thermoelectric conversion material produced
  • the high-purity silicon of the present invention is produced by sintering silicon waste at a high density in a non-oxidizing atmosphere by a discharge plasma sintering method.
  • the silicon waste is sintered at a sintering temperature of about 900 ° C. or higher.
  • the silicon temperature of the silicon waste can be efficiently increased by setting the sintering temperature to about 900 ° C. or higher.
  • the silicon waste is sintered at a sintering temperature of about 900 ° C.
  • the silicon purity of the silicon waste can be increased more efficiently by setting the sintering temperature to about 900 ° C.
  • the silicon waste is sintered with a holding time of about 1800 seconds or more.
  • the silicon purity of the silicon waste can be increased efficiently by setting the holding time to about 1800 ° C. or higher.
  • the high-purity silicon of the present invention is produced by dissolving the silicon waste sintered by the discharge plasma sintering method in a vacuum or a non-oxidizing atmosphere.
  • the high-purity silicon of the present invention is produced by dissolving the silicon waste at a melting temperature of 1800 ° C. or higher.
  • the impurities are vaporized and the impurities in the silicon waste can be removed.
  • the high-purity silicon of the present invention is produced by dissolving the silicon waste under a reduced pressure of 1.3 ⁇ 10 ⁇ 1 Pa or less.
  • the impurities are vaporized and the impurities in the silicon waste can be removed.
  • the high-purity silicon of the present invention is produced by melting the silicon waste with either a melting furnace or a discharge plasma sintering apparatus.
  • the high-purity silicon of the present invention is produced when the silicon waste contains SiO and SiC.
  • the reduction action of silicon oxide can be promoted by the reaction between SiO and SiC resulting in the redox action.
  • the high-purity silicon of the present invention is produced by mixing and dissolving a C-based material or a Ca-based material in the silicon waste.
  • the reduction action of silicon oxide can be promoted by using a system substance or a Ca system substance as a reducing agent.
  • the high-purity silicon of the present invention is produced by spraying an inert gas on the surface of the dissolved silicon waste.
  • slag is concentrated near the surface of the silicon waste by blowing an inert gas onto the surface of the dissolved silicon waste, so that high-purity silicon is produced by separating this slag portion. can do.
  • the high-purity silicon of the present invention is produced by cooling the dissolved silicon waste and performing an annealing treatment in a hydrogen atmosphere.
  • thermoelectric conversion material according to the present invention is characterized by being produced by mixing silicon waste with an Fe component and sintering in a non-oxidizing atmosphere by a discharge plasma sintering method.
  • thermoelectric conversion material is generated by rapidly heating, holding a temperature for a short time, and rapidly cooling a mixture of silicon and Fe by a discharge plasma sintering method, and silicon waste is used.
  • a thermoelectric conversion material can be obtained simply and inexpensively.
  • thermoelectric conversion material according to the present invention is characterized in that the silicon waste is a silicon waste in which silicon is highly purified by sintering in a non-oxidizing atmosphere by a discharge plasma sintering method.
  • thermoelectric conversion material Since there is no need to reduce silicon waste with a reducing agent, a thermoelectric conversion material can be obtained simply and inexpensively.
  • the mixture of the silicon waste and the Fe component is a mixture obtained by solidifying the silicon waste with an aggregating agent containing Fe.
  • thermoelectric conversion material by using Fe contained in the flocculant as a part of the thermoelectric conversion material, silicon waste aggregated by the flocculant can be used as it is, and a process of separately mixing an iron component Therefore, a thermoelectric conversion material can be obtained at low cost.
  • thermoelectric conversion material according to the present invention is characterized in that the aggregating agent containing Fe is iron chloride, iron sulfide, or a combination thereof.
  • Fe contained in the flocculant can be used as a part of the thermoelectric conversion material.
  • thermoelectric conversion material an Al component is mixed with the silicon waste, and the mixture of the silicon waste and the Al component is a mixture obtained by solidifying the silicon waste with a flocculant containing Al. It is characterized by that.
  • thermoelectric conversion material since the Al contained in the flocculant is used as a substitution metal element when generating the p-type thermoelectric conversion material, a separate Al doping process is not required. Aggregated silicon waste can be used as it is, and a thermoelectric conversion material can be obtained at low cost.
  • thermoelectric conversion material according to the present invention is characterized in that the aggregating agent containing Al is aluminum oxide, aluminum sulfide, polyaluminum chloride, or a combination thereof.
  • Al contained in the flocculant can be used as a part of the thermoelectric conversion material.
  • thermoelectric conversion material according to the present invention is characterized in that the silicon waste is generated from a production process of a silicon wafer.
  • the silicon waste is generated by a cleaning process, and is a silicon waste mainly composed of pure water and Si.
  • thermoelectric conversion material high-purity silicon waste can be used as it is, and silicon waste can be reused easily and inexpensively to obtain a thermoelectric conversion material.
  • the silicon waste is a silicon waste solid-liquid separated by centrifugation, squeezing separation, sedimentation separation, floating separation, or a combination thereof.
  • thermoelectric conversion material can be obtained.
  • thermoelectric conversion material according to the present invention is characterized in that the non-oxidizing atmosphere is any one of vacuum, nitrogen gas, argon gas, hydrogen gas, or a mixed gas thereof.
  • thermoelectric conversion material by sintering in a non-oxidizing atmosphere, an oxidation reaction can be prevented in the process of forming the Fe—Si based thermoelectric conversion material, and a suitable thermoelectric conversion material can be obtained.
  • thermoelectric conversion material according to the present invention is characterized in that the sintering is performed at a pressure of 10 to 100 MPa and a heating / sintering temperature of 500 to 2000 ° C.
  • thermoelectric conversion material a non-equilibrium phase having a high figure of merit as a thermoelectric conversion material is formed, and ⁇ -FeSi 2 having a ⁇ phase is generated.
  • thermoelectric conversion material The method for producing a thermoelectric conversion material according to the present invention is characterized in that it is produced by mixing silicon waste with an Fe component and sintering it in a non-oxidizing atmosphere by a discharge plasma sintering method.
  • thermoelectric conversion material is generated by rapidly heating, holding a temperature for a short time, and rapidly cooling a mixture of silicon and Fe by a discharge plasma sintering method, and silicon waste is used.
  • a thermoelectric conversion material can be obtained simply and inexpensively.
  • silicon waste is dissolved in a vacuum or non-oxidizing atmosphere to remove impurities in silicon waste, reduce silicon oxide, and reuse silicon waste easily and inexpensively.
  • the high-purity silicon can be produced.
  • thermoelectric conversion material is produced by rapid heating, holding temperature for a short time, and quenching a mixture of silicon and Fe by a discharge plasma sintering method, and silicon waste is By using it, a thermoelectric conversion material can be obtained simply and inexpensively.
  • FIG. 1 is a basic configuration diagram of a discharge plasma sintering apparatus used in this example. The sintering process by the discharge plasma sintering apparatus used in this example is shown.
  • the high-purity silicon according to the embodiment of the present invention is produced by discharge plasma sintering (SPS) and melting silicon waste in a vacuum or non-oxidizing atmosphere.
  • SPS discharge plasma sintering
  • the spark plasma sintering method is a method in which an on-off DC pulse voltage / current is applied to a green compact, and a sintered body is produced by a discharge phenomenon that occurs between the powder particles.
  • metals, ceramics, etc. can be sintered at high density.
  • Sintering is mainly performed by heat generation using graphite as a resistor, but the pulse electric field promotes the movement / diffusion of ions, vacancies and dislocations. Can be sintered.
  • sintering by the discharge plasma sintering method a uniform high-quality sintered body can be easily obtained with uniform pressure by dispersion of discharge points.
  • Silicon waste may be sintered by a discharge plasma sintering method without separating the liquid fraction from the solid fraction. Further, silicon waste may be sintered by a discharge plasma sintering method without using a sintering aid.
  • the present inventor uses a discharge plasma sintering apparatus and a melting furnace to treat silicon waste mainly composed of SiO or SiO 2 at a high temperature in a vacuum or a non-oxidizing atmosphere, thereby converting high-purity silicon from silicon waste.
  • a discharge plasma sintering apparatus it has been found that high purity silicon can be produced by sintering silicon waste using a discharge plasma sintering apparatus.
  • high-purity silicon can be obtained efficiently by setting the sintering temperature to about 900 ° C. or higher (preferably about 900 ° C.). It was also found that high-purity silicon can be obtained efficiently by setting the holding time to 1800 seconds or longer.
  • the silicon waste sintered using the discharge plasma sintering is melted and processed at a high temperature, so that SiO is gasified and components containing Al, Mg, Ca, P, and B which are impurities It has been found that even higher purity silicon can be obtained by gasifying and removing the gasified impurities. And when the slag was isolate
  • FIG. 1 is a graph showing the relationship between sintering temperature and component concentration of silicon waste.
  • the horizontal axis represents the sintering temperature, and the vertical axis represents the component concentration in the silicon waste.
  • the silicon waste (silicon grinding sludge) was dehydrated and then sintered using a discharge plasma sintering apparatus.
  • the sintering temperatures are 900 ° C. (1173 K), 1000 ° C. (1273 K), 1100 ° C. (1373 K), and 1200 ° C. (1473 K), and the holding temperature is 1800 seconds (1800 s).
  • FIG. 1 it is clear that the silicon concentration is increased by about 20% by sintering silicon waste at a sintering temperature of about 900 ° C.
  • the silicon waste sintered by the discharge plasma sintering apparatus is melted and processed at a high temperature.
  • FIG. 2 is a graph showing the relationship between the heating temperature of silicon waste and the component concentration of impurity gas.
  • the horizontal axis represents the heating temperature
  • the vertical axis represents the component concentration of the impurity gas generated from the silicon waste.
  • SiO gas is generated when the heating temperature is about 1400 ° C., and a large amount of SiO gas is stably generated at 1800 ° C. or higher.
  • a gas amount due to Fe, Al, and Mg impurity elements is generated in addition to the SiO gas.
  • the heating temperature is 2400 ° C. or higher, all of impurity gases of SiO, Fe, Al, and Mg are stably generated in large quantities.
  • SiO, Fe, Al, and Mg impurity gases can be removed by dissolving silicon waste at a heating temperature (melting temperature) of 1800 ° C. or higher.
  • a heating temperature melting temperature
  • 2400 ° C. or higher a large amount of impurity gas can be removed.
  • impurities can be removed from the silicon waste, and high-purity silicon can be generated.
  • the silicon waste sintered by the discharge plasma sintering apparatus is melted using a vacuum induction melting furnace.
  • Vacuum induction melting furnaces used for casting special steels and non-ferrous metals are characterized by homogeneous melting by electromagnetic stirring, and can be melted in a reduced-pressure atmosphere or in vacuum using high-frequency induction heating and vacuum technology. It is.
  • a crucible is installed in a chamber of a vacuum induction melting furnace, and silicon wafer cutting waste is melted in this crucible.
  • the crucible is made of carbon.
  • the silicon wafer cutting waste is silicon waste containing SiO, but may contain SiC.
  • SiC is used for a grindstone for polishing a silicon wafer, and may be contained in cutting waste of the silicon wafer. In this case, SiC functions as a reducing agent that reduces SiO.
  • High temperature heat treatment of silicon waste is performed by making the inside of a vacuum induction melting furnace chamber a vacuum or a non-oxidizing atmosphere.
  • a vacuum or a non-oxidizing atmosphere By using a vacuum or a non-oxidizing atmosphere, the oxidation of silicon can be prevented and the reduction of silicon oxide can be promoted. Therefore, by treating silicon waste at high temperature in a vacuum or non-oxidizing atmosphere, impurities in the silicon waste can be removed and silicon oxide can be reduced efficiently, and silicon waste can be reused easily and inexpensively. High purity silicon can be produced.
  • the degree of vacuum may be 1.3 ⁇ 10 ⁇ 1 or less.
  • nitrogen gas, argon gas, hydrogen gas, or a mixed gas thereof may be used.
  • the silicon waste is heated at a high temperature by setting the inside of the chamber of the vacuum induction melting furnace to a vacuum degree of 1.3 ⁇ 10 ⁇ 1 to 1.3 ⁇ 10 ⁇ 2 .
  • the heating temperature When the heating temperature is increased by a vacuum induction melting furnace, SiO gas begins to be generated at 1400-1500 ° C. And from about 1800 degreeC, the gas amount resulting from impurity elements, such as Fe, Al, and Ca, increases. Further, the impurity elements include P and B, and the amount of gas resulting from these impurities also increases.
  • the heating temperature is 1850 ° C. or higher. More preferably, the heating temperature is 2000 ° C. or higher.
  • silicon waste mainly composed of SiO or SiO 2 is treated at a high temperature in a vacuum or a non-oxidizing atmosphere to dissolve the silicon waste and produce high-purity silicon. Can do. This high purity silicon is useful as solar cell silicon.
  • a C-based substance or a Ca-based substance may be used as the reducing agent.
  • the reduction effect of silicon waste can be promoted by mixing and dissolving the C-based material or Ca-based material in the silicon waste.
  • the C-based material include carbon powder and silicon carbide.
  • the Ca-based material include calcium oxide, calcium chloride, and calcium carbonate.
  • an inert gas may be sprayed on the surface of the dissolved silicon waste.
  • an inert gas By blowing an inert gas on the surface of the dissolved silicon waste, the slag is concentrated near the surface of the silicon waste. Therefore, by separating this slag portion, higher purity silicon can be generated. .
  • the ingot in which the molten silicon is cooled may be annealed in a hydrogen atmosphere.
  • high-purity silicon can be generated by removing impurities (such as O and N) in silicon waste and reducing silicon oxide.
  • thermoelectric conversion material concerning the 2nd Embodiment of this invention is demonstrated in detail, this invention is not limited only to this embodiment.
  • a silicon waste material is mixed with an iron component, and sintered at a high density in a non-oxidizing atmosphere by a discharge plasma sintering (hereinafter abbreviated as SPS method) method, thereby obtaining a thermoelectric conversion material. Is generated.
  • SPS method discharge plasma sintering
  • the silicon waste is mixed with the iron component such that the Fe to Si elemental ratio is substantially 1: 1.8-3, more preferably the Fe to Si elemental ratio is substantially
  • the silicon waste is mixed with the iron component so as to be 1: 2.
  • a substitution metal element may be included in addition to Fe and Si.
  • the replacement metal element semiconductor properties are imparted by substituting a part of iron or silicon, and Mn, Cr, V, and Al for forming a p-type semiconductor, or an n-type semiconductor Co, Ni, Pt, etc. for When a substitution metal element is included, the element ratio of the substitution metal element is, for example, 0.5 to 10%.
  • the SPS method used in this embodiment is a method in which an on-off DC pulse voltage / current is applied to a green compact, and a sintered body is produced by a discharge phenomenon that occurs in the powder particle gap.
  • Metals, ceramics, and the like can be sintered at high density in a short time and at low temperatures. Sintering is mainly performed by heat generation using graphite as a resistor, but the pulse electric field promotes the movement / diffusion of ions, vacancies and dislocations. Can be sintered. Silicon waste cannot be sintered by conventional methods and has been deposited in landfills or burned in incinerators.
  • silicon waste which has conventionally been difficult to reuse, is sintered by the SPS method without separating the liquid fraction from the solid fraction, thereby obtaining a thermoelectric conversion material easily and inexpensively. be able to.
  • a uniform high-quality sintered body can be easily obtained with uniform pressure by dispersion of discharge points.
  • a sintering aid is not particularly required.
  • a non-oxidizing atmosphere that is any one of vacuum, nitrogen gas, argon gas, hydrogen gas, or a mixed gas thereof is used. This is because by using a non-oxidizing atmosphere, an oxidation reaction is prevented in the process of forming the Fe—Si thermoelectric conversion material, and a reduction reaction occurring in the sintering process is promoted. Due to the reducing action of the graphite part in the SPS method, silicon in silicon waste is highly purified, and a high-quality thermoelectric conversion material can be obtained. In addition, a reduction effect is accelerated
  • silicon waste whose silicon has been purified in advance is mixed with the iron component, and further in the non-oxidizing atmosphere by the SPS method. It may be sintered.
  • a reduction action occurs in the graphite portion of the discharge plasma sintering apparatus, and a high-quality thermoelectric conversion material material can be obtained, and it is not necessary to reduce silicon waste with a reducing agent.
  • a conversion material can be obtained.
  • thermoelectric conversion material having a purity of 70% or more is obtained from oxidized silicon powder having a purity of about 40% by the SPS method, and this high-purity silicon waste and an iron component are mixed, By further sintering with, a high-quality thermoelectric conversion material can be obtained.
  • sintering is performed in a range where the pressure applied in the SPS method is 10 to 100 MPa and the heating / sintering temperature is 500 to 2000 ° C.
  • the pressurizing pressure and the heating / sintering temperature can be freely selected within a suitable range in order to obtain a high-quality thermoelectric conversion material.
  • the silicon wafer production process in the present embodiment includes, for example, a silicon wafer discarded as a nonconforming product in addition to silicon scrap generated by slicing, dicing, grinding and polishing of a silicon ingot or a silicon substrate.
  • the silicon waste is generated by the cleaning process, and may be silicon waste mainly composed of pure water and Si.
  • the cleaning waste liquid contains silicon particles or silicon pieces together with pure water. Conventionally, this cleaning waste liquid has been discarded.
  • this cleaning waste liquid can be used as silicon waste to obtain a low-cost thermoelectric conversion material. If cleaning waste liquid mainly composed of pure water and Si is used, high-purity silicon can be used as a raw material for thermoelectric conversion materials as it is.
  • the silicon waste may be a silicon waste obtained by solid-liquid separation of the slurry waste liquid or the like by centrifugal separation, squeezing separation, sedimentation separation, floating separation, or a combination thereof in addition to the washing waste water.
  • impurities such as glycol and oil are removed to extract silicon, and by using this silicon, a high-quality thermoelectric conversion material can be obtained.
  • the mixture of silicon waste and iron component may be a mixture obtained by solidifying silicon waste with a flocculant containing Fe as a component.
  • the flocculant containing Fe as a component may be any of iron chloride, iron sulfide, or a combination thereof.
  • the flocculant is iron chloride FeCl 2
  • the SiPS contained in the silicon waste reacts with FeCl 2 by rapid heating, holding the temperature for a short time, and quenching by the SPS method, and the non-equilibrium phase And ⁇ -FeSi 2 having a ⁇ phase is produced.
  • a thermoelectric conversion material improves, a thermoelectric conversion material can be obtained simply and inexpensively by utilizing silicon waste.
  • the Fe—Si system has crystal forms such as Fe 3 Si, Fe 2 Si, Fe 5 Si 3 , FeSi, ⁇ -FeSi 2 , and ⁇ -FeSi 2 depending on the composition ratio.
  • ⁇ -FeSi 2 that is stable in a low temperature region exhibits semiconductor characteristics with a forbidden band width of about 0.85 eV, and is suitable as a thermoelectric conversion material.
  • the flocculant FeCl 3 , FeCl 3 , FeS, Fe 2 S 3 , FeS 2 and the like are used in addition to FeCl 2 .
  • thermoelectric conversion material As described above, by using Fe contained in the flocculant as a raw material of the thermoelectric conversion material, silicon waste aggregated with the flocculant can be used as it is, and a process of separately mixing an iron component becomes unnecessary. Therefore, a thermoelectric conversion material can be obtained at low cost.
  • the solidified silicon waste may be sintered by the SPS method without separating the liquid fraction.
  • SiCl 4 is produced as a reaction byproduct.
  • SiCl 4 is a gas component, it does not stay or accumulate in the reaction region, and there is an advantage that the possibility of inhibiting the reaction is small.
  • the mixture of silicon waste and Al component is a mixture of silicon waste solidified with an aggregating agent containing Al.
  • the flocculant containing Al as a component may be any of aluminum oxide, aluminum sulfide, polyaluminum chloride, or a combination thereof.
  • the components of the flocculant Al 2 O 3 , Al 2 (SO 4 ) 3 , [Al 2 (OH n ) Cl 6-n ] m (1 ⁇ n ⁇ 5, m ⁇ 10) and the like are used.
  • thermoelectric conversion material By using Al contained in the flocculant as a replacement metal element when generating a p-type thermoelectric conversion material, a separate Al doping treatment is not required, and the flocculant is agglomerated by the flocculant.
  • the silicon waste can be used as it is, and a thermoelectric conversion material can be obtained at low cost.
  • FIG. 3 shows a basic configuration diagram of the discharge plasma sintering apparatus 10 used in this embodiment.
  • the discharge plasma sintering apparatus 10 applies a pulsed large current at a low voltage while pressing the sample set on the sintering die 9 with the upper punch 7 and the lower punch 8, and generates a discharge plasma generated by a spark discharge phenomenon. Use it for sintering.
  • SPS-520 manufactured by SPS Shintex Co., Ltd.
  • a graphite die having an inner diameter of about 20 mm and a height of 40 mm is used as the sintering die, and a carbon sheet having a thickness of 0.2 mm is used for peeling the sample from the sintering die.
  • the silicon waste recovered from the production process of the silicon wafer is mixed with the iron component so that the Fe to Si element ratio is 1: 2, without separating the liquid fraction from the solid fraction, It was accommodated in a sintered die as it was, pressurized with 40 MPa through a die punch, and further heated with a pulse current to 800 ° C., held for 5 minutes, then turned off and cooled.
  • the degree of vacuum in the sintering chamber during sintering was about 3 Pa.
  • thermoelectric conversion material according to the present invention is produced by performing rapid heating, short-time temperature holding, and rapid cooling on a mixture of silicon and Fe by a discharge plasma sintering method. By using waste, a thermoelectric conversion material can be obtained simply and inexpensively.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Silicon Compounds (AREA)

Abstract

Provided is a high grade silicon obtained by removing impurities from silicon waste and reducing silicon oxide so as to easily reuse the silicon waste at a reasonable cost.  The high grade silicon is generated by high-density sintering the silicon waste by the discharge plasma sintering method in a non-oxidizing atmosphere.

Description

高純度シリコンおよび熱電変換材料High purity silicon and thermoelectric conversion materials
　本発明は高純度シリコンに関し、特に、シリコンウエハーの生産過程などから生じるシリコン廃棄物を再利用して生成される高純度シリコンに関する。また、本発明は、熱電変換材料に関するものであり、特に、シリコンウエハーの生産過程などから生じるシリコン廃棄物を再利用して生成される熱電変換材料に関する。 The present invention relates to high-purity silicon, and more particularly to high-purity silicon produced by reusing silicon waste generated from the production process of silicon wafers. The present invention also relates to a thermoelectric conversion material, and more particularly to a thermoelectric conversion material produced by reusing silicon waste generated from a production process of a silicon wafer.
　半導体基板原料のシリコン単結晶は、シリカの還元、モノシランへの転化、水素還元、単結晶シリコン引き上げのプロセス経て製造され、多大なエネルギーを消費している、更に半導体基板であるシリコンチップは、シリコン単結晶をスライスしてシリコンウエハーとして、ラッピング、ポリッシングの工程を経て、最終的にダイシングされることによって得られるが、シリコン単結晶からシリコンチップへの収率はわずか３０％であり、残りの７０％はシリコンスラッジとして廃棄物として処理されている。 The silicon single crystal of the semiconductor substrate raw material is manufactured through processes of silica reduction, conversion to monosilane, hydrogen reduction, single crystal silicon pulling process, and consumes a lot of energy. Furthermore, the silicon chip as the semiconductor substrate is silicon The single crystal is obtained by slicing a single crystal as a silicon wafer through wrapping and polishing steps, and finally dicing. The yield from the silicon single crystal to the silicon chip is only 30%, and the remaining 70 % Is treated as waste as silicon sludge.
　また、特許文献１に示すように、太陽電池用シリコンの製造方法において、半導体産業で発生するシリコン廃棄物を出発原料として、これをまず溶融し、次いで底部に貫通孔を有し、珪素化合物を主成分とする物質から構成したろ過容器に珪素化合物を主成分とする物質をフィルター材として充填したろ過装置でろ過処理し、次いで該ろ過処理後に酸化処理を施し、次いで減圧処理を施した後、一方向凝固させることを特徴とする太陽電池用シリコンの製造方法が開示されている。 Moreover, as shown in Patent Document 1, in a method for producing silicon for solar cells, silicon waste generated in the semiconductor industry is used as a starting material, and this is first melted, and then has a through-hole at the bottom, and a silicon compound. Filtration is carried out with a filtration device filled with a substance mainly composed of a silicon compound as a filter material in a filtration container composed of the substance as a main component, then subjected to an oxidation treatment after the filtration treatment, and then subjected to a decompression treatment, A method for producing silicon for solar cells, characterized by unidirectional solidification, is disclosed.
特開平５－２７０８１４号公報JP-A-5-270814 特開２００２－１６７２８０号公報JP 2002-167280 A
　しかしながら、このようなシリコンスラッジ廃棄物は、埋立地に堆積されるか、あるいは焼却炉で燃やされているが、埋立地にスラッジを堆積すると、オイルやグリコールが土壌中に滲出する危険があり、環境問題となっている。また、焼却炉での焼却は、シリコンスラッジ中のシリコン粉末が汚染された二酸化ケイ素に変換され、土壌中に堆積されることになる。このように、シリコン粉末廃棄物は、環境汚染を伴うため、環境対策のためのコスト増が課題となっている。さらに、集積回路と太陽電池パネルの需要の高まりと共に、シリコン粉末廃棄物による環境汚染の懸念が、今後ますます高まることが予想される。したがって、環境対策コストを抑えつつ、大量のシリコンスラッジ廃棄物を簡易かつ安全に再利用する方法が特に必要とされている。 However, such silicon sludge waste is deposited in a landfill or burned in an incinerator, but if sludge is deposited in a landfill, there is a risk that oil and glycol will leach into the soil, It has become an environmental problem. Moreover, incineration in an incinerator converts silicon powder in silicon sludge into contaminated silicon dioxide and deposits it in the soil. Thus, since silicon powder waste is accompanied by environmental pollution, an increase in cost for environmental measures is a problem. Furthermore, with the increasing demand for integrated circuits and solar panels, the concern about environmental pollution from silicon powder waste is expected to increase further in the future. Therefore, there is a particular need for a method for easily and safely reusing a large amount of silicon sludge waste while reducing environmental measures costs.
　また、特許文献１に開示されている発明は、ろ過処理を施さなければならないため、ろ過処理に時間やコストを要し、工業的な再利用としては採算性が伴わない。 Further, since the invention disclosed in Patent Document 1 must be subjected to a filtration treatment, the filtration treatment requires time and cost, and is not accompanied by profitability as industrial reuse.
　したがって、シリコン廃棄物を簡易かつ安価に再利用して、高純度シリコンを得ることができれば、環境対策を考慮したシリコンスラッジの再利用に大きく貢献することができる。 Therefore, if silicon waste can be reused easily and inexpensively to obtain high-purity silicon, it can greatly contribute to the reuse of silicon sludge in consideration of environmental measures.
　また、熱電変換材料の原料として、スラリー廃液に含まれるシリコンスラッジから高純度シリコンを生成するためには、沈降分離又は濾過などによって、シリコン粒子からなる固体フラクションを液体フラクションであるグリコールまたはオイルから分離分離した後、Fe（鉄）やAl（アルミニウム）などの不純物元素を除去しなければならず、プロセスが煩雑である。また、シリコン廃棄物は酸化が進んでいるため、高純度シリコンを生成するためには、シリコン廃棄物を還元剤により還元しなければならず、プロセスがさらに煩雑となる。このように、シリコンスラッジから熱電変換材料の原料となる高純度シリコンを得るためには、プロセスが煩雑となるのでコストを要し、工業的な再利用としては採算性が伴わない。 In addition, in order to produce high-purity silicon from silicon sludge contained in slurry waste liquid as a raw material for thermoelectric conversion materials, a solid fraction consisting of silicon particles is separated from glycol or oil, which is a liquid fraction, by sedimentation separation or filtration. After the separation, impurity elements such as Fe (iron) and Al (aluminum) must be removed, and the process is complicated. Further, since silicon waste is being oxidized, in order to produce high-purity silicon, the silicon waste must be reduced with a reducing agent, which further complicates the process. Thus, in order to obtain high-purity silicon as a raw material for the thermoelectric conversion material from silicon sludge, the process becomes complicated and costs are required, and there is no profitability for industrial reuse.
　さらに、溶解法を用いて、シリコンと鉄の混合物からFe-Si系熱電変換材料を生成することはできず、Fe-Si系熱電変換材料を生成するためには、溶解法により形成された金属相（ε相、α相）をさらに長時間熱処理することにより、Fe-Si系熱電変換材料の半導体相（β相）が得られる。このように、溶解法では、時間やコストを要するため、工業的な再利用としては採算性が伴わない。 Furthermore, it is not possible to produce a Fe-Si thermoelectric conversion material from a mixture of silicon and iron using the melting method. To produce a Fe-Si thermoelectric conversion material, the metal formed by the melting method is used. The semiconductor phase (β phase) of the Fe—Si-based thermoelectric conversion material can be obtained by further heat-treating the phases (ε phase, α phase) for a longer time. As described above, the dissolution method requires time and cost, and is not accompanied by profitability as industrial reuse.
　したがって、シリコン廃棄物を簡易かつ安価に再利用して、熱電変換材料を得ることができれば、環境対策を考慮したシリコンスラッジの再利用に大きく貢献することができる。 Therefore, if silicon waste can be reused easily and inexpensively to obtain a thermoelectric conversion material, it can greatly contribute to the reuse of silicon sludge in consideration of environmental measures.
　本発明は、従来の問題を解決するためになされたもので、シリコン廃棄物を利用して生成される高純度シリコンを提供することを目的とする。また、本発明は、シリコン廃棄物を利用して生成される熱電変換材料を提供することを目的とする。 The present invention has been made to solve the conventional problems, and an object of the present invention is to provide high-purity silicon produced using silicon waste. Moreover, an object of this invention is to provide the thermoelectric conversion material produced | generated using a silicon waste.
　本発明の高純度シリコンは、シリコン廃棄物を放電プラズマ焼結法によって非酸化性雰囲気において高密度に焼結することにより生成されることを特徴とする高純度シリコン。 The high-purity silicon of the present invention is produced by sintering silicon waste at a high density in a non-oxidizing atmosphere by a discharge plasma sintering method.
　この構成によれば、放電プラズマ焼結法を用いることで、シリコン廃棄物を簡易かつ安価に再利用して、高純度シリコンを生成することができる。 According to this configuration, by using the discharge plasma sintering method, silicon waste can be reused easily and inexpensively to produce high-purity silicon.
　本発明の高純度シリコンでは、約９００℃以上の焼結温度で前記シリコン廃棄物を焼結する。 In the high-purity silicon of the present invention, the silicon waste is sintered at a sintering temperature of about 900 ° C. or higher.
　この構成によれば、焼結温度を約９００℃以上にすることで、効率的にシリコン廃棄物のシリコン純度を上げることができる。 According to this configuration, the silicon temperature of the silicon waste can be efficiently increased by setting the sintering temperature to about 900 ° C. or higher.
　本発明の高純度シリコンでは、約９００℃の焼結温度で前記シリコン廃棄物を焼結する。 In the high-purity silicon of the present invention, the silicon waste is sintered at a sintering temperature of about 900 ° C.
　この構成によれば、焼結温度を約９００℃にすることで、さらに効率的にシリコン廃棄物のシリコン純度を上げることができる。 According to this configuration, the silicon purity of the silicon waste can be increased more efficiently by setting the sintering temperature to about 900 ° C.
　本発明の高純度シリコンでは、約１８００秒以上の保持時間で前記シリコン廃棄物を焼結する。 In the high-purity silicon of the present invention, the silicon waste is sintered with a holding time of about 1800 seconds or more.
　この構成によれば、保持時間を約１８００℃以上にすることで、効率的にシリコン廃棄物のシリコン純度を上げることができる。 According to this configuration, the silicon purity of the silicon waste can be increased efficiently by setting the holding time to about 1800 ° C. or higher.
　本発明の高純度シリコンは、放電プラズマ焼結法により焼結された前記シリコン廃棄物を真空または非酸化性雰囲気において溶解することにより生成される。 The high-purity silicon of the present invention is produced by dissolving the silicon waste sintered by the discharge plasma sintering method in a vacuum or a non-oxidizing atmosphere.
　この構成によれば、放電プラズマ焼結法により焼結され、高純度化されたシリコン廃棄物における不純物を除去するとともに、シリコン廃棄物を簡易かつ安価に再利用して、さらに高純度なシリコンを生成することができる。 According to this configuration, impurities in silicon waste that has been sintered and purified by the discharge plasma sintering method can be removed, and silicon waste can be reused easily and inexpensively to obtain higher purity silicon. Can be generated.
　本発明の高純度シリコンは、１８００℃以上の溶解温度で前記シリコン廃棄物を溶解することにより生成される。 The high-purity silicon of the present invention is produced by dissolving the silicon waste at a melting temperature of 1800 ° C. or higher.
　この構成によれば、シリコン廃棄物を高温処理することで、不純物が気化し、シリコン廃棄物における不純物を除去することができる。 According to this configuration, by treating the silicon waste at a high temperature, the impurities are vaporized and the impurities in the silicon waste can be removed.
　本発明の高純度シリコンは、１．３×１０－１Ｐａ以下の減圧下において前記シリコン廃棄物を溶解することにより生成される。 The high-purity silicon of the present invention is produced by dissolving the silicon waste under a reduced pressure of 1.3 × 10 −1 Pa or less.
　この構成によれば、減圧下で溶解処理を行うことで、不純物が気化し、シリコン廃棄物における不純物を除去することができる。 According to this configuration, by performing the dissolution treatment under reduced pressure, the impurities are vaporized and the impurities in the silicon waste can be removed.
　本発明の高純度シリコンは、溶解炉および放電プラズマ焼結装置の何れかにより前記シリコン廃棄物を溶解することにより生成される。 The high-purity silicon of the present invention is produced by melting the silicon waste with either a melting furnace or a discharge plasma sintering apparatus.
　この構成によれば、溶解炉および放電プラズマ焼結装置を用いることで、高温処理が可能となり、不純物の排除および酸化シリコンの還元を促進することができる。 According to this configuration, by using a melting furnace and a discharge plasma sintering apparatus, high-temperature processing can be performed, and the elimination of impurities and the reduction of silicon oxide can be promoted.
　本発明の高純度シリコンは、前記シリコン廃棄物はＳｉＯおよびＳｉＣを含むことにより生成される。 The high-purity silicon of the present invention is produced when the silicon waste contains SiO and SiC.
　この構成によれば、ＳｉＯとＳｉＣが反応して酸化還元作用が生じることで、酸化シリコンの還元作用を促進することができる。 According to this configuration, the reduction action of silicon oxide can be promoted by the reaction between SiO and SiC resulting in the redox action.
　本発明の高純度シリコンは、前記シリコン廃棄物にＣ系物質またはＣａ系物質を混合して溶解することにより生成される。 The high-purity silicon of the present invention is produced by mixing and dissolving a C-based material or a Ca-based material in the silicon waste.
　この構成によれば、系物質またはＣａ系物質を還元剤として用いることで、酸化シリコンの還元作用を促進することができる。 According to this configuration, the reduction action of silicon oxide can be promoted by using a system substance or a Ca system substance as a reducing agent.
　本発明の高純度シリコンは、溶解した前記シリコン廃棄物の表面に不活性ガスを吹き付けることにより生成される。 The high-purity silicon of the present invention is produced by spraying an inert gas on the surface of the dissolved silicon waste.
　この構成によれば、溶解したシリコン廃棄物の表面に不活性ガスを吹き付けることで、シリコン廃棄物の表面付近でスラグが濃縮されるため、このスラグ部分を分離することにより、高純度シリコンを生成することができる。 According to this configuration, slag is concentrated near the surface of the silicon waste by blowing an inert gas onto the surface of the dissolved silicon waste, so that high-purity silicon is produced by separating this slag portion. can do.
　本発明の高純度シリコンは、溶解した前記シリコン廃棄物を冷却し、水素雰囲気において焼鈍処理を行うことにより生成される。 The high-purity silicon of the present invention is produced by cooling the dissolved silicon waste and performing an annealing treatment in a hydrogen atmosphere.
　この構成によれば、水素雰囲気において焼鈍処理を行うことで、シリコン廃棄物における不純物を除去するとともに、酸化シリコンを還元することにより、高純度シリコンを生成することができる。 According to this configuration, it is possible to produce high-purity silicon by removing impurities in silicon waste and reducing silicon oxide by performing an annealing process in a hydrogen atmosphere.
　本発明にかかる熱電変換材料は、シリコン廃棄物をFe成分と混合し、放電プラズマ焼結法によって非酸化性雰囲気において焼結することにより生成されることを特徴とする。 The thermoelectric conversion material according to the present invention is characterized by being produced by mixing silicon waste with an Fe component and sintering in a non-oxidizing atmosphere by a discharge plasma sintering method.
　この構成によれば、放電プラズマ焼結法により、シリコンとFeの混合物に対して急加熱、短時間温度保持、および急冷を行うことで熱電変換材料が生成される共に、シリコン廃棄物を利用することにより、簡易かつ安価に熱電変換材料を得ることができる。 According to this configuration, a thermoelectric conversion material is generated by rapidly heating, holding a temperature for a short time, and rapidly cooling a mixture of silicon and Fe by a discharge plasma sintering method, and silicon waste is used. Thus, a thermoelectric conversion material can be obtained simply and inexpensively.
　本発明にかかる熱電変換材料は、前記シリコン廃棄物は、放電プラズマ焼結法によって非酸化性雰囲気において焼結することにより、シリコンが高純度化されたシリコン廃棄物であることを特徴とする。 The thermoelectric conversion material according to the present invention is characterized in that the silicon waste is a silicon waste in which silicon is highly purified by sintering in a non-oxidizing atmosphere by a discharge plasma sintering method.
　この構成によれば、放電プラズマ焼結法によって、放電プラズマ焼結装置のグラファイト部において還元作用が生じ、この還元作用によって高純度化されたシリコン廃棄物を熱電変換材料の原料として利用することにより、シリコン廃棄物を還元剤により還元する必要がなくなるため、簡易かつ安価に熱電変換材料を得ることができる。 According to this configuration, a reduction action occurs in the graphite portion of the discharge plasma sintering apparatus by the discharge plasma sintering method, and silicon waste purified by this reduction action is used as a raw material for the thermoelectric conversion material. Since there is no need to reduce silicon waste with a reducing agent, a thermoelectric conversion material can be obtained simply and inexpensively.
　本発明にかかる熱電変換材料では、前記シリコン廃棄物と前記Fe成分の混合物は、Feを含む凝集剤により、前記シリコン廃棄物を固液化した混合物であることを特徴とする。 In the thermoelectric conversion material according to the present invention, the mixture of the silicon waste and the Fe component is a mixture obtained by solidifying the silicon waste with an aggregating agent containing Fe.
　この構成によれば、凝集剤に含まれるFeを、熱電変換材料の一部として利用することにより、凝集剤により凝集されたシリコン廃棄物をそのまま利用することができ、別途鉄成分を混合する処理が不要となるため、低コストで熱電変換材料を得ることができる。 According to this configuration, by using Fe contained in the flocculant as a part of the thermoelectric conversion material, silicon waste aggregated by the flocculant can be used as it is, and a process of separately mixing an iron component Therefore, a thermoelectric conversion material can be obtained at low cost.
　本発明にかかる熱電変換材料では、前記Feを含む凝集剤は、塩化鉄、硫化鉄、もしくはこれらの組み合わせの何れかであることを特徴とする。 The thermoelectric conversion material according to the present invention is characterized in that the aggregating agent containing Fe is iron chloride, iron sulfide, or a combination thereof.
　この構成によれば、凝集剤に含まれるFeを、熱電変換材料の一部として利用することができる。 According to this configuration, Fe contained in the flocculant can be used as a part of the thermoelectric conversion material.
　本発明にかかる熱電変換材料では、前記シリコン廃棄物にAl成分を混合し、前記シリコン廃棄物と前記Al成分の混合物は、Alを含む凝集剤により、前記シリコン廃棄物を固液化した混合物であることを特徴とする。 In the thermoelectric conversion material according to the present invention, an Al component is mixed with the silicon waste, and the mixture of the silicon waste and the Al component is a mixture obtained by solidifying the silicon waste with a flocculant containing Al. It is characterized by that.
　この構成によれば、凝集剤に含まれるAlを、p型の熱電変換材料を生成する際の置換用金属元素として利用することにより、別途Alをドープする処理が不要となるため、凝集剤により凝集されたシリコン廃棄物をそのまま利用することができ、低コストで熱電変換材料を得ることができる。 According to this configuration, since the Al contained in the flocculant is used as a substitution metal element when generating the p-type thermoelectric conversion material, a separate Al doping process is not required. Aggregated silicon waste can be used as it is, and a thermoelectric conversion material can be obtained at low cost.
　本発明にかかる熱電変換材料では、前記Alを含む凝集剤は、酸化アルミニウム、硫化アルミニウム、ポリ塩化アルミニウム、もしくはこれらの組み合わせの何れかであることを特徴とする。 The thermoelectric conversion material according to the present invention is characterized in that the aggregating agent containing Al is aluminum oxide, aluminum sulfide, polyaluminum chloride, or a combination thereof.
　この構成によれば、凝集剤に含まれるAlを、熱電変換材料の一部として利用することができる。 According to this configuration, Al contained in the flocculant can be used as a part of the thermoelectric conversion material.
　本発明にかかる熱電変換材料では、前記シリコン廃棄物は、シリコンウエハーの生産過程から生じるものであることを特徴とする。 The thermoelectric conversion material according to the present invention is characterized in that the silicon waste is generated from a production process of a silicon wafer.
　この構成によれば、シリコン廃棄物を利用することにより、大量のシリコンスラッジ廃棄物を簡易かつ安価に処理することができる。 According to this configuration, a large amount of silicon sludge waste can be treated easily and inexpensively by using silicon waste.
　本発明にかかる熱電変換材料では、前記シリコン廃棄物は、洗浄工程により生じるものであって、主に純水とSiから成るシリコン廃棄物であることを特徴とする。 In the thermoelectric conversion material according to the present invention, the silicon waste is generated by a cleaning process, and is a silicon waste mainly composed of pure water and Si.
　この構成によれば、高純度のシリコン廃棄物をそのまま利用することができ、シリコン廃棄物を簡易かつ安価に再利用して、熱電変換材料を得ることができる。 According to this configuration, high-purity silicon waste can be used as it is, and silicon waste can be reused easily and inexpensively to obtain a thermoelectric conversion material.
　本発明にかかる熱電変換材料では、前記シリコン廃棄物は、遠心分離、圧搾分離、沈降分離、浮上分離、もしくはこれらの組み合わせにより固液分離されたシリコン廃棄物であることを特徴とする。 In the thermoelectric conversion material according to the present invention, the silicon waste is a silicon waste solid-liquid separated by centrifugation, squeezing separation, sedimentation separation, floating separation, or a combination thereof.
　この構成によれば、低純度のシリコン廃棄物であっても、そのまま利用することができ、シリコン廃棄物を高純度化する処理が不要となるため、低コストの熱電変換材料を得ることができる。 According to this configuration, even a low-purity silicon waste can be used as it is, and a process for increasing the purity of the silicon waste is not required, so that a low-cost thermoelectric conversion material can be obtained. .
　本発明にかかる熱電変換材料では、前記非酸化性雰囲気が、真空、窒素ガス、アルゴンガス、水素ガス、もしくはこれらの混合ガスの何れかであることを特徴とする。 The thermoelectric conversion material according to the present invention is characterized in that the non-oxidizing atmosphere is any one of vacuum, nitrogen gas, argon gas, hydrogen gas, or a mixed gas thereof.
　この構成によれば、非酸化性雰囲気において焼結することにより、Fe-Si系熱電変換材料が形成される過程において酸化反応を防ぐことができ、好適な熱電変換材料を得ることができる。 According to this configuration, by sintering in a non-oxidizing atmosphere, an oxidation reaction can be prevented in the process of forming the Fe—Si based thermoelectric conversion material, and a suitable thermoelectric conversion material can be obtained.
　本発明にかかる熱電変換材料では、加圧圧力が１０～１００MPa、加熱・焼結温度が５００～２０００℃の範囲で前記焼結を行うことを特徴とする。 The thermoelectric conversion material according to the present invention is characterized in that the sintering is performed at a pressure of 10 to 100 MPa and a heating / sintering temperature of 500 to 2000 ° C.
　この構成によれば、熱電変換材料としての性能指数が高い非平衡相が形成され、β相を有するβ-FeSi２が生成される。 According to this configuration, a non-equilibrium phase having a high figure of merit as a thermoelectric conversion material is formed, and β-FeSi 2 having a β phase is generated.
　本発明にかかる熱電変換材料生成方法は、シリコン廃棄物をFe成分と混合し、放電プラズマ焼結法によって非酸化性雰囲気において焼結することにより生成することを特徴とする。 The method for producing a thermoelectric conversion material according to the present invention is characterized in that it is produced by mixing silicon waste with an Fe component and sintering it in a non-oxidizing atmosphere by a discharge plasma sintering method.
　この構成によれば、放電プラズマ焼結法により、シリコンとFeの混合物に対して急加熱、短時間温度保持、および急冷を行うことで熱電変換材料が生成されると共に、シリコン廃棄物を利用することにより、簡易かつ安価に熱電変換材料を得ることができる。 According to this configuration, a thermoelectric conversion material is generated by rapidly heating, holding a temperature for a short time, and rapidly cooling a mixture of silicon and Fe by a discharge plasma sintering method, and silicon waste is used. Thus, a thermoelectric conversion material can be obtained simply and inexpensively.
　本発明によれば、シリコン廃棄物を真空または非酸化性雰囲気において溶解することにより、シリコン廃棄物における不純物を除去するとともに、酸化シリコンを還元し、シリコン廃棄物を簡易かつ安価に再利用して、高純度シリコンを生成することができるという効果を有する。 According to the present invention, silicon waste is dissolved in a vacuum or non-oxidizing atmosphere to remove impurities in silicon waste, reduce silicon oxide, and reuse silicon waste easily and inexpensively. The high-purity silicon can be produced.
　また、本発明によれば、放電プラズマ焼結法により、シリコンとFeの混合物に対して急加熱、短時間温度保持、および急冷を行うことで熱電変換材料が生成されると共に、シリコン廃棄物を利用することにより、簡易かつ安価に熱電変換材料を得ることができる。 Further, according to the present invention, a thermoelectric conversion material is produced by rapid heating, holding temperature for a short time, and quenching a mixture of silicon and Fe by a discharge plasma sintering method, and silicon waste is By using it, a thermoelectric conversion material can be obtained simply and inexpensively.
シリコン廃棄物の焼結温度と成分濃度との関係を表したグラフである。It is a graph showing the relationship between the sintering temperature and component concentration of silicon waste. シリコン廃棄物の加熱温度と不純物ガス発生量との関係を表したグラフである。It is the graph showing the relationship between the heating temperature of silicon waste, and the amount of impurity gas generation. 本実施例で用いた放電プラズマ焼結装置の基本構成図を示したものである。1 is a basic configuration diagram of a discharge plasma sintering apparatus used in this example. 本実施例で用いた放電プラズマ焼結装置による焼結過程を示したものである。The sintering process by the discharge plasma sintering apparatus used in this example is shown.
（第１の実施の形態）
　以下、本発明の第１の実施の形態の高純度シリコンについて説明する。 (First embodiment)
Hereinafter, the high purity silicon according to the first embodiment of the present invention will be described.
　本発明の実施の形態にかかる高純度シリコンは、シリコン廃棄物を真空または非酸化性雰囲気において放電プラズマ焼結（ＳＰＳ）および溶解することにより生成される。 The high-purity silicon according to the embodiment of the present invention is produced by discharge plasma sintering (SPS) and melting silicon waste in a vacuum or non-oxidizing atmosphere.
　放電プラズマ焼結法は、圧粉体にオン－オフ直流パルス電圧・電流を印加し、粉体粒子間隙で起こる放電現象により焼結体を作製する方法であり、従来よりも短時間、低温度で、金属、セラミックスなどを高密度に焼結することができる。焼結は主に、グラファイト（黒鉛）を抵抗体とする発熱によって行われるが、パルス電場は、イオン、空孔及び転位の移動・拡散を促進するため、通常の方法では焼結できない粉体でも焼結することができる。また、放電プラズマ焼結法により焼結することで、放電点の分散による均等加圧で、均質高品位の焼結体が容易に得ることができる。シリコン廃棄物を、固体フラクションから液体フラクションを分離することなく、放電プラズマ焼結法により焼結してもよい。また、シリコン廃棄物を、焼結助剤を用いずに放電プラズマ焼結法により焼結してもよい。 The spark plasma sintering method is a method in which an on-off DC pulse voltage / current is applied to a green compact, and a sintered body is produced by a discharge phenomenon that occurs between the powder particles. Thus, metals, ceramics, etc. can be sintered at high density. Sintering is mainly performed by heat generation using graphite as a resistor, but the pulse electric field promotes the movement / diffusion of ions, vacancies and dislocations. Can be sintered. In addition, by sintering by the discharge plasma sintering method, a uniform high-quality sintered body can be easily obtained with uniform pressure by dispersion of discharge points. Silicon waste may be sintered by a discharge plasma sintering method without separating the liquid fraction from the solid fraction. Further, silicon waste may be sintered by a discharge plasma sintering method without using a sintering aid.
　本発明者は、放電プラズマ焼結装置および溶解炉を用いて、ＳｉＯまたはＳｉＯ２を主成分とするシリコン廃棄物を真空または非酸化性雰囲気において高温処理することにより、シリコン廃棄物から高純度シリコンを生成する技術について鋭意研究を行った。この結果、シリコン廃棄物を、放電プラズマ焼結装置を用いて焼結することにより、高純度シリコンを生成できることを見出した。特に、焼結温度を約９００℃以上（好ましくは約９００℃）にすることで、効率的に高純度シリコンが得られることを見出した。また、保持時間を１８００秒以上にすることで、効率的に高純度シリコンが得られることを見出した。さらに、放電プラズマ焼結を用いて焼結されたシリコン廃棄物を、溶解して高温処理することにより、ＳｉＯがガス化するとともに、不純物であるＡｌ、Ｍｇ、Ｃａ、Ｐ、およびＢを含む成分もガス化し、このガス化した不純物を除去できることから、さらに高純度なシリコンが得られることを見出した。そして、ガス化した不純物が除去された溶解金属（溶解シリコン）を冷却したインゴットからスラグを分離した場合に、５Ｎ以上の高純度シリコンが得られることを見出した。 The present inventor uses a discharge plasma sintering apparatus and a melting furnace to treat silicon waste mainly composed of SiO or SiO 2 at a high temperature in a vacuum or a non-oxidizing atmosphere, thereby converting high-purity silicon from silicon waste. We conducted intensive research on the technology to generate As a result, it has been found that high purity silicon can be produced by sintering silicon waste using a discharge plasma sintering apparatus. In particular, it has been found that high-purity silicon can be obtained efficiently by setting the sintering temperature to about 900 ° C. or higher (preferably about 900 ° C.). It was also found that high-purity silicon can be obtained efficiently by setting the holding time to 1800 seconds or longer. Furthermore, the silicon waste sintered using the discharge plasma sintering is melted and processed at a high temperature, so that SiO is gasified and components containing Al, Mg, Ca, P, and B which are impurities It has been found that even higher purity silicon can be obtained by gasifying and removing the gasified impurities. And when the slag was isolate | separated from the ingot which cooled the melt | dissolved metal (melt | dissolved silicon) from which the gasified impurity was removed, it discovered that 5N or more high purity silicon was obtained.
　図１は、シリコン廃棄物の焼結温度と成分濃度との関係を表したグラフである。横軸は、焼結温度を表し、縦軸は、シリコン廃棄物における成分濃度を表す。シリコン廃棄物（シリコン研削スラッジ）に脱水処理を施した後、放電プラズマ焼結装置を用いて焼結処理を施した。焼結温度は、９００℃（１１７３Ｋ）、１０００℃（１２７３Ｋ）、１１００℃（１３７３Ｋ）、および１２００℃（１４７３Ｋ）であり、保持温度は１８００秒（１８００ｓ）である。図１によれば、放電プラズマ焼結法により約９００℃以上の焼結温度でシリコン廃棄物を焼結することにより、Ｓｉの濃度が約２０質量％上昇することが明らかになり、高純度シリコンが得られることが明らかになった。特に、約９００℃の焼結温度でシリコン廃棄物を焼結することで、濃度が８５．６質量％のＳｉ焼結体を得られた。 FIG. 1 is a graph showing the relationship between sintering temperature and component concentration of silicon waste. The horizontal axis represents the sintering temperature, and the vertical axis represents the component concentration in the silicon waste. The silicon waste (silicon grinding sludge) was dehydrated and then sintered using a discharge plasma sintering apparatus. The sintering temperatures are 900 ° C. (1173 K), 1000 ° C. (1273 K), 1100 ° C. (1373 K), and 1200 ° C. (1473 K), and the holding temperature is 1800 seconds (1800 s). According to FIG. 1, it is clear that the silicon concentration is increased by about 20% by sintering silicon waste at a sintering temperature of about 900 ° C. or higher by the discharge plasma sintering method. It became clear that can be obtained. In particular, by sintering silicon waste at a sintering temperature of about 900 ° C., a Si sintered body having a concentration of 85.6% by mass was obtained.
　次に、放電プラズマ焼結装置により焼結されたシリコン廃棄物を、溶解して高温処理する。 Next, the silicon waste sintered by the discharge plasma sintering apparatus is melted and processed at a high temperature.
　図２は、シリコン廃棄物の加熱温度と不純物ガスの成分濃度との関係を表したグラフである。横軸は、加熱温度を表し、縦軸は、シリコン廃棄物から発生する不純物ガスの成分濃度を表す。図１に示すように、加熱温度が約１４００℃になるとＳｉＯガスが発生し、１８００℃以上で安定的に大量のＳｉＯガスが発生する。また、加熱温度が１８００℃以上になると、ＳｉＯガスの他、Ｆｅ、Ａｌ、およびＭｇの不純物元素に起因するガス量が発生する。特に、加熱温度が２４００℃以上になると、ＳｉＯ、Ｆｅ、Ａｌ、およびＭｇの何れの不純物ガスも安定的に大量に発生する。 FIG. 2 is a graph showing the relationship between the heating temperature of silicon waste and the component concentration of impurity gas. The horizontal axis represents the heating temperature, and the vertical axis represents the component concentration of the impurity gas generated from the silicon waste. As shown in FIG. 1, SiO gas is generated when the heating temperature is about 1400 ° C., and a large amount of SiO gas is stably generated at 1800 ° C. or higher. In addition, when the heating temperature is 1800 ° C. or higher, a gas amount due to Fe, Al, and Mg impurity elements is generated in addition to the SiO gas. In particular, when the heating temperature is 2400 ° C. or higher, all of impurity gases of SiO, Fe, Al, and Mg are stably generated in large quantities.
　したがって、１８００℃以上の加熱温度（溶解温度）でシリコン廃棄物を溶解することにより、ＳｉＯ、Ｆｅ、Ａｌ、およびＭｇの不純物ガスを除去することができる。特に、加熱温度を２４００℃以上にすることで、大量の不純物ガスを除去することができる。このように、シリコン廃棄物を高温加熱処理することにより、シリコン廃棄物から不純物を除去することができ、高純度シリコンを生成することができる。 Therefore, SiO, Fe, Al, and Mg impurity gases can be removed by dissolving silicon waste at a heating temperature (melting temperature) of 1800 ° C. or higher. In particular, by setting the heating temperature to 2400 ° C. or higher, a large amount of impurity gas can be removed. As described above, by treating the silicon waste at a high temperature, impurities can be removed from the silicon waste, and high-purity silicon can be generated.
　本実施の形態では、真空誘導溶解炉を用いて、放電プラズマ焼結装置により焼結されたシリコン廃棄物を溶解する。特殊鋼、非鉄金属の鋳造に利用される真空誘導溶解炉は、電磁撹拌作用により均質な溶解ができることを特徴としており、高周波誘導加熱と真空技術により、減圧雰囲気下および真空中での溶解が可能である。また、高活性材料の溶解法には、坩堝からの不純物混入を避けるため、水冷坩堝を使用するスカル溶解法や、誘導磁場により空中浮遊させて溶解するレビテーション溶解法などがある。 In this embodiment, the silicon waste sintered by the discharge plasma sintering apparatus is melted using a vacuum induction melting furnace. Vacuum induction melting furnaces used for casting special steels and non-ferrous metals are characterized by homogeneous melting by electromagnetic stirring, and can be melted in a reduced-pressure atmosphere or in vacuum using high-frequency induction heating and vacuum technology. It is. Moreover, in order to avoid mixing impurities from the crucible, there are a skull melting method using a water-cooled crucible and a levitation melting method in which it is suspended in the air by an induction magnetic field to dissolve the highly active material.
　本実施の形態では、真空誘導溶解炉のチャンバー内に坩堝を設置し、この坩堝でシリコンウエハーの切削屑を溶解する。坩堝はカーボン製である。また、シリコンウエハーの切削屑は、ＳｉＯを含むシリコン廃棄物であるが、ＳｉＣが含まれていてもよい。ＳｉＣは、シリコンウエハーを研磨する砥石に用いられ、シリコンウエハーの切削屑に含まれる場合がある。この場合、ＳｉＣはＳｉＯを還元する還元剤として機能する。 In this embodiment, a crucible is installed in a chamber of a vacuum induction melting furnace, and silicon wafer cutting waste is melted in this crucible. The crucible is made of carbon. Further, the silicon wafer cutting waste is silicon waste containing SiO, but may contain SiC. SiC is used for a grindstone for polishing a silicon wafer, and may be contained in cutting waste of the silicon wafer. In this case, SiC functions as a reducing agent that reduces SiO.
　シリコン廃棄物の高温加熱処理は、真空誘導溶解炉のチャンバー内を真空または非酸化性雰囲気にすることによって行われる。真空または非酸化性雰囲気にすることにより、シリコンの酸化を防止するとともに、酸化シリコンの還元を促進することができる。したがって、真空または非酸化性雰囲気においてシリコン廃棄物を高温処理することによって、シリコン廃棄物における不純物を除去するとともに、酸化シリコンを効率的に還元でき、シリコン廃棄物を簡易かつ安価に再利用して、高純度シリコンを生成することができる。 High temperature heat treatment of silicon waste is performed by making the inside of a vacuum induction melting furnace chamber a vacuum or a non-oxidizing atmosphere. By using a vacuum or a non-oxidizing atmosphere, the oxidation of silicon can be prevented and the reduction of silicon oxide can be promoted. Therefore, by treating silicon waste at high temperature in a vacuum or non-oxidizing atmosphere, impurities in the silicon waste can be removed and silicon oxide can be reduced efficiently, and silicon waste can be reused easily and inexpensively. High purity silicon can be produced.
　なお、チャンバー内を真空にする場合は、１．３×１０－１以下の真空度であればよい。また、チャンバー内を非酸化性雰囲気にする場合は、窒素ガス、アルゴンガス、水素ガス、もしくはこれらの混合ガスを用いればよい。本実施の形態では、真空誘導溶解炉のチャンバー内を１．３×１０－１～１．３×１０－２の真空度にすることによって、シリコン廃棄物の高温加熱処理を行う。 Note that when the chamber is evacuated, the degree of vacuum may be 1.3 × 10 −1 or less. In addition, in the case where the inside of the chamber is set to a non-oxidizing atmosphere, nitrogen gas, argon gas, hydrogen gas, or a mixed gas thereof may be used. In the present embodiment, the silicon waste is heated at a high temperature by setting the inside of the chamber of the vacuum induction melting furnace to a vacuum degree of 1.3 × 10 −1 to 1.3 × 10 −2 .
　真空誘導溶解炉によって、加熱温度を上昇させていくと、１４００～１５００℃でＳｉＯガスが発生し始める。そして、約１８００℃からＦｅ、Ａｌ、およびＣａなどの不純物元素に起因するガス量が増加する。また、不純物元素にはＰおよびＢも含まれ、これらの不純物に起因するガス量も増加する。好ましくは、加熱温度は１８５０℃以上である。さらに好ましくは、加熱温度は２０００℃以上である。 When the heating temperature is increased by a vacuum induction melting furnace, SiO gas begins to be generated at 1400-1500 ° C. And from about 1800 degreeC, the gas amount resulting from impurity elements, such as Fe, Al, and Ca, increases. Further, the impurity elements include P and B, and the amount of gas resulting from these impurities also increases. Preferably, the heating temperature is 1850 ° C. or higher. More preferably, the heating temperature is 2000 ° C. or higher.
　本実施の形態では、加熱温度を１９００℃まで上昇させた後、１８０分間の還元反応を行い、不純物ガスを除去する。不純物ガスを除去した溶解シリコンを冷却し、インゴットを生成する。インゴットの最終凝固部のスラグ部分を切断除去することで、５Ｎの高純度シリコンが得られた。 In this embodiment, after raising the heating temperature to 1900 ° C., a reduction reaction is performed for 180 minutes to remove the impurity gas. The dissolved silicon from which the impurity gas has been removed is cooled to generate an ingot. By cutting and removing the slag portion of the final solidified portion of the ingot, 5N high-purity silicon was obtained.
　このように、溶解炉を用いて、ＳｉＯまたはＳｉＯ２を主成分とするシリコン廃棄物を真空または非酸化性雰囲気において高温処理することにより、シリコン廃棄物を溶解させ、高純度シリコンを生成することができる。この高純度シリコンは、太陽電池用シリコンとして有用である。 In this way, by using a melting furnace, silicon waste mainly composed of SiO or SiO 2 is treated at a high temperature in a vacuum or a non-oxidizing atmosphere to dissolve the silicon waste and produce high-purity silicon. Can do. This high purity silicon is useful as solar cell silicon.
　以上、本発明にかかる実施の形態について説明したが、本発明はこれらに限定されるものではなく、請求項に記載された範囲内において変更・変形することが可能である。 As mentioned above, although embodiment concerning this invention was described, this invention is not limited to these, It is possible to change and change within the range described in the claim.
　例えば、還元剤としてＣ系物質またはＣａ系物質を用いてもよい。シリコン廃棄物にＣ系物質またはＣａ系物質を混合して溶解することにより、シリコン廃棄物の還元作用を促進することができる。Ｃ系物質としては、炭素粉末および炭化ケイ素などがある。また、Ｃａ系物質として、カルシウム酸化物、塩化カルシウム、および炭酸カルシウムなどがある。 For example, a C-based substance or a Ca-based substance may be used as the reducing agent. The reduction effect of silicon waste can be promoted by mixing and dissolving the C-based material or Ca-based material in the silicon waste. Examples of the C-based material include carbon powder and silicon carbide. Examples of the Ca-based material include calcium oxide, calcium chloride, and calcium carbonate.
　また、溶解したシリコン廃棄物の表面に不活性ガスを吹き付けてもよい。溶解したシリコン廃棄物の表面に不活性ガスを吹き付けることで、シリコン廃棄物の表面付近でスラグが濃縮されるため、このスラグ部分を分離することにより、さらに高純度のシリコンを生成することができる。 Further, an inert gas may be sprayed on the surface of the dissolved silicon waste. By blowing an inert gas on the surface of the dissolved silicon waste, the slag is concentrated near the surface of the silicon waste. Therefore, by separating this slag portion, higher purity silicon can be generated. .
　また、溶解シリコンを冷却したインゴットを、水素雰囲気において焼鈍処理を行ってもよい。水素雰囲気において焼鈍処理を行うことで、シリコン廃棄物における不純物（ＯおよびＮなど）を除去するとともに、酸化シリコンを還元することにより、高純度シリコンを生成することができる。 Further, the ingot in which the molten silicon is cooled may be annealed in a hydrogen atmosphere. By performing the annealing process in a hydrogen atmosphere, high-purity silicon can be generated by removing impurities (such as O and N) in silicon waste and reducing silicon oxide.
（第２の実施の形態）
　以下、本発明の第２の実施の形態にかかる熱電変換材料について詳細に説明するが、本発明はかかる実施の形態のみに限定されるものではない。 (Second Embodiment)
Hereinafter, although the thermoelectric conversion material concerning the 2nd Embodiment of this invention is demonstrated in detail, this invention is not limited only to this embodiment.
　本発明の実施の形態では、シリコン廃棄物を鉄成分と混合し、放電プラズマ焼結（以下、SPS法と略記する）法によって非酸化性雰囲気において高密度に焼結することにより、熱電変換材料を生成する。 In the embodiment of the present invention, a silicon waste material is mixed with an iron component, and sintered at a high density in a non-oxidizing atmosphere by a discharge plasma sintering (hereinafter abbreviated as SPS method) method, thereby obtaining a thermoelectric conversion material. Is generated.
　好適には、FeとSiの元素比が実質的に１：１．８～３となるように、シリコン廃棄物を鉄成分と混合し、さらに好適には、FeとSiの元素比が実質的に１：２となるように、シリコン廃棄物を鉄成分と混合する。本実施の形態では、FeおよびSiの他、置換用金属元素が含まれてもよい。ここで、置換用金属元素としては、鉄またはシリコンの一部分を置換することによって半導体特性を付与するものであって、p型半導体とするためのMn、Cr、V、およびAlや、n型半導体とするためのCo、Ni、およびPtなどが相当する。置換用金属元素を含む場合、置換用金属元素の元素比率は、例えば０．５～１０％である。 Preferably, the silicon waste is mixed with the iron component such that the Fe to Si elemental ratio is substantially 1: 1.8-3, more preferably the Fe to Si elemental ratio is substantially The silicon waste is mixed with the iron component so as to be 1: 2. In the present embodiment, a substitution metal element may be included in addition to Fe and Si. Here, as the replacement metal element, semiconductor properties are imparted by substituting a part of iron or silicon, and Mn, Cr, V, and Al for forming a p-type semiconductor, or an n-type semiconductor Co, Ni, Pt, etc. for When a substitution metal element is included, the element ratio of the substitution metal element is, for example, 0.5 to 10%.
　本実施の形態において使用されるSPS法は、圧粉体にオン－オフ直流パルス電圧・電流を印加し、粉体粒子間隙で起こる放電現象により焼結体を作製する方法であり、従来よりも短時間、低温度で、金属、セラミックスなどを高密度に焼結することができる。焼結は主に、グラファイト（黒鉛）を抵抗体とする発熱によって行われるが、パルス電場は、イオン、空孔及び転位の移動・拡散を促進するため、通常の方法では焼結できない粉体でも焼結することができる。シリコン廃棄物は従来の方法では、焼結することができず、これまで埋立地に堆積されるか、あるいは焼却炉で燃やされていた。本実施の形態においては、従来再利用が困難とされていたシリコン廃棄物を、固体フラクションから液体フラクションを分離することなく、SPS法により焼結することで、熱電変換材料を簡易かつ安価に得ることができる。また、SPS法により焼結することで、放電点の分散による均等加圧で、均質高品位の焼結体が容易に得ることができる。本実施の形態における焼結に際しては、特に、焼結助剤を必要としない。 The SPS method used in this embodiment is a method in which an on-off DC pulse voltage / current is applied to a green compact, and a sintered body is produced by a discharge phenomenon that occurs in the powder particle gap. Metals, ceramics, and the like can be sintered at high density in a short time and at low temperatures. Sintering is mainly performed by heat generation using graphite as a resistor, but the pulse electric field promotes the movement / diffusion of ions, vacancies and dislocations. Can be sintered. Silicon waste cannot be sintered by conventional methods and has been deposited in landfills or burned in incinerators. In this embodiment, silicon waste, which has conventionally been difficult to reuse, is sintered by the SPS method without separating the liquid fraction from the solid fraction, thereby obtaining a thermoelectric conversion material easily and inexpensively. be able to. In addition, by sintering by the SPS method, a uniform high-quality sintered body can be easily obtained with uniform pressure by dispersion of discharge points. In sintering in the present embodiment, a sintering aid is not particularly required.
　本実施の形態では、SPS法において、真空、窒素ガス、アルゴンガス、水素ガス、もしくはこれらの混合ガスの何れかである非酸化性雰囲気を用いる。これは、非酸化性雰囲気を用いることによって、Fe-Si系熱電変換材料が形成される過程において酸化反応を防ぐと共に、焼結処理の過程において生じる還元反応を促進するためである。SPS法におけるグラファイト部の還元作用によって、シリコン廃棄物中のシリコンが高純度化され、高品質な熱電変換材料を得ることができる。なお、焼結温度が高温になるほど、還元作用が促進される。このように、本実施の形態においては、従来再利用が困難とされていたシリコン廃棄物を、SPS法により焼結することで、簡易かつ安価にシリコンを高純度化させ、高品質な熱電変換材料を得ることができる。 In this embodiment, in the SPS method, a non-oxidizing atmosphere that is any one of vacuum, nitrogen gas, argon gas, hydrogen gas, or a mixed gas thereof is used. This is because by using a non-oxidizing atmosphere, an oxidation reaction is prevented in the process of forming the Fe—Si thermoelectric conversion material, and a reduction reaction occurring in the sintering process is promoted. Due to the reducing action of the graphite part in the SPS method, silicon in silicon waste is highly purified, and a high-quality thermoelectric conversion material can be obtained. In addition, a reduction effect is accelerated | stimulated, so that sintering temperature becomes high. As described above, in the present embodiment, silicon waste, which has been difficult to reuse in the past, is sintered by the SPS method, so that silicon can be easily and inexpensively purified, and high-quality thermoelectric conversion. Material can be obtained.
　したがって、本実施の形態では、SPS法によって非酸化性雰囲気において焼結することにより、予めシリコンが高純度化されたシリコン廃棄物を鉄成分と混合して、非酸化性雰囲気においてSPS法でさらに焼結してもよい。この場合、放電プラズマ焼結装置のグラファイト部において還元作用が生じ、高品質な熱電変換材料の原料を得ることができ、シリコン廃棄物を還元剤により還元する必要がなくなるため、簡易かつ安価に熱電変換材料を得ることができる。なお、本実施の形態では、純度４０％程度の酸化されたシリコン粉末から、SPS法によって、純度７０％以上の高純度シリコンが得られ、この高純度シリコン廃棄物と鉄成分と混合して、でさらに焼結することにより、高品質な熱電変換材料を得ることができる。 Therefore, in this embodiment, by sintering in a non-oxidizing atmosphere by the SPS method, silicon waste whose silicon has been purified in advance is mixed with the iron component, and further in the non-oxidizing atmosphere by the SPS method. It may be sintered. In this case, a reduction action occurs in the graphite portion of the discharge plasma sintering apparatus, and a high-quality thermoelectric conversion material material can be obtained, and it is not necessary to reduce silicon waste with a reducing agent. A conversion material can be obtained. In this embodiment, high-purity silicon having a purity of 70% or more is obtained from oxidized silicon powder having a purity of about 40% by the SPS method, and this high-purity silicon waste and an iron component are mixed, By further sintering with, a high-quality thermoelectric conversion material can be obtained.
　本実施の形態では、SPS法の焼結における加圧圧力が、１０～１００MPaの範囲であり、加熱・焼結温度が５００～２０００℃の範囲で焼結を行う。ただし、加圧圧力および加熱・焼結温度は、高品質な熱電変換材料を得るために、好適な範囲を自由に選択できる。 In the present embodiment, sintering is performed in a range where the pressure applied in the SPS method is 10 to 100 MPa and the heating / sintering temperature is 500 to 2000 ° C. However, the pressurizing pressure and the heating / sintering temperature can be freely selected within a suitable range in order to obtain a high-quality thermoelectric conversion material.
　本実施の形態の特徴の１つは、シリコンウエハーの生産過程から生じたシリコン廃棄物を利用することである。したがって、シリコン廃棄物について詳細に説明する。本実施の形態におけるシリコンウエハーの生産過程とは、例えば、シリコンインゴットやシリコン基板のスライシング、ダイシング、グラインディングおよびポリッシングなどにより生じたシリコン屑の他、不適合品として廃棄されるシリコンウエハーも含まれる。 One feature of the present embodiment is that silicon waste generated from the production process of silicon wafers is used. Therefore, the silicon waste will be described in detail. The silicon wafer production process in the present embodiment includes, for example, a silicon wafer discarded as a nonconforming product in addition to silicon scrap generated by slicing, dicing, grinding and polishing of a silicon ingot or a silicon substrate.
　また、シリコン廃棄物は、洗浄工程により生じるものであって、主に純水とSiから成るシリコン廃棄物であってよい。シリコンウエハーの生産過程で、シリコンウエハーなどを洗浄するために純水が用いられる。この場合、洗浄廃液には、純水と共にシリコン粒子またはシリコン片が含まれる。従来は、この洗浄廃液は廃棄されていた。本実施の形態では、この洗浄廃液をシリコン廃棄物として利用し、低コストの熱電変換材料を得ることができる。主に純水とSiから成る洗浄廃液を用いれば、高純度シリコンをそのまま熱電変換材料の原料として利用することができる。 Further, the silicon waste is generated by the cleaning process, and may be silicon waste mainly composed of pure water and Si. In the production process of silicon wafers, pure water is used to clean the silicon wafers and the like. In this case, the cleaning waste liquid contains silicon particles or silicon pieces together with pure water. Conventionally, this cleaning waste liquid has been discarded. In the present embodiment, this cleaning waste liquid can be used as silicon waste to obtain a low-cost thermoelectric conversion material. If cleaning waste liquid mainly composed of pure water and Si is used, high-purity silicon can be used as a raw material for thermoelectric conversion materials as it is.
　また、シリコン廃棄物は、洗浄廃水の他、スラリー廃液などを遠心分離、圧搾分離、沈降分離、浮上分離、もしくはこれらの組み合わせにより固液分離したシリコン廃棄物であってもよい。これらの処理によって、グリコールやオイルなどの不純物を取り除くことで、シリコンを抽出し、このシリコンを利用することによって、高品質な熱電変換材料を得ることができる。 Further, the silicon waste may be a silicon waste obtained by solid-liquid separation of the slurry waste liquid or the like by centrifugal separation, squeezing separation, sedimentation separation, floating separation, or a combination thereof in addition to the washing waste water. Through these treatments, impurities such as glycol and oil are removed to extract silicon, and by using this silicon, a high-quality thermoelectric conversion material can be obtained.
　また、シリコン廃棄物と鉄成分の混合物は、Feを成分とする凝集剤により、シリコン廃棄物を固液化した混合物であってもよい。この場合、Feを成分とする凝集剤は、塩化鉄、硫化鉄、もしくはこれらの組み合わせの何れかであればよい。 Further, the mixture of silicon waste and iron component may be a mixture obtained by solidifying silicon waste with a flocculant containing Fe as a component. In this case, the flocculant containing Fe as a component may be any of iron chloride, iron sulfide, or a combination thereof.
　例えば、凝集剤が塩化鉄FeCl２である場合、SPS法により急加熱、短時間温度保持、および急冷を行うことで、シリコン廃棄物に含まれるSiとFeCl２とが反応を起こし、非平衡相が形成され、β相を有するβ-FeSi２が生成される。これにより、熱電変換材料としての性能指数が向上すると共に、シリコン廃棄物を利用することにより、簡易かつ安価に熱電変換材料を得ることができる。 For example, when the flocculant is iron chloride FeCl 2 , the SiPS contained in the silicon waste reacts with FeCl 2 by rapid heating, holding the temperature for a short time, and quenching by the SPS method, and the non-equilibrium phase And β-FeSi 2 having a β phase is produced. Thereby, while the figure of merit as a thermoelectric conversion material improves, a thermoelectric conversion material can be obtained simply and inexpensively by utilizing silicon waste.
　Fe-Si系には、その組成比に応じて、Fe３Si、Fe２Si、Fe５Si３、FeSi、α-FeSi２、およびβ-FeSi２などの結晶形態が存在する。これらの結晶形態のうち、低温域で安定であるβ-FeSi２は禁制帯幅が約０．８５eVの半導体特性を示し、熱電変換材料として好適である。凝集剤としては、FeCl２の他、FeCl３、FeS、Fe２S３、およびFeS２などが用いられる。 The Fe—Si system has crystal forms such as Fe 3 Si, Fe 2 Si, Fe 5 Si 3 , FeSi, α-FeSi 2 , and β-FeSi 2 depending on the composition ratio. Among these crystal forms, β-FeSi 2 that is stable in a low temperature region exhibits semiconductor characteristics with a forbidden band width of about 0.85 eV, and is suitable as a thermoelectric conversion material. As the flocculant, FeCl 3 , FeCl 3 , FeS, Fe 2 S 3 , FeS 2 and the like are used in addition to FeCl 2 .
　このように、凝集剤に含まれるFeを熱電変換材料の原材料として利用することにより、凝集剤で凝集されたシリコン廃棄物をそのまま利用することができ、別途鉄成分を混合する処理が不要となるため、低コストで熱電変換材料を得ることができる。この場合、固液化したシリコン廃棄物は、液体フラクションを分離することなく、SPS法により焼結してもよい。 As described above, by using Fe contained in the flocculant as a raw material of the thermoelectric conversion material, silicon waste aggregated with the flocculant can be used as it is, and a process of separately mixing an iron component becomes unnecessary. Therefore, a thermoelectric conversion material can be obtained at low cost. In this case, the solidified silicon waste may be sintered by the SPS method without separating the liquid fraction.
　また、凝集剤として塩化鉄を用いれば、反応副生成物としてSiCl４を生じる。この場合、SiCl４はガス成分であるため、反応領域に滞留・堆積せず、反応を阻害する可能性が小さいという利点もある。 Moreover, if iron chloride is used as the flocculant, SiCl 4 is produced as a reaction byproduct. In this case, since SiCl 4 is a gas component, it does not stay or accumulate in the reaction region, and there is an advantage that the possibility of inhibiting the reaction is small.
　また、p型の熱電変換材料を生成する際の置換用金属元素としてAlを用いる場合、シリコン廃棄物とAl成分の混合物は、Alを含む凝集剤により、シリコン廃棄物を固液化した混合物であってもよい。この場合、Alを成分とする凝集剤は、酸化アルミニウム、硫化アルミニウム、ポリ塩化アルミニウム、もしくはこれらの組み合わせの何れかであればよい。凝集剤の成分としては、Al２O３、Al２（SO４）３、および［Al２（OHｎ）Cl６－ｎ］ｍ（１≦ｎ≦５、ｍ≦１０）などが用いられる。 In addition, when Al is used as a metal element for substitution when producing a p-type thermoelectric conversion material, the mixture of silicon waste and Al component is a mixture of silicon waste solidified with an aggregating agent containing Al. May be. In this case, the flocculant containing Al as a component may be any of aluminum oxide, aluminum sulfide, polyaluminum chloride, or a combination thereof. As the components of the flocculant, Al 2 O 3 , Al 2 (SO 4 ) 3 , [Al 2 (OH n ) Cl 6-n ] m (1 ≦ n ≦ 5, m ≦ 10) and the like are used.
　このように、凝集剤に含まれるAlを、p型の熱電変換材料を生成する際の置換用金属元素として利用することにより、別途Alをドープする処理が不要となるため、凝集剤により凝集されたシリコン廃棄物をそのまま利用することができ、低コストで熱電変換材料を得ることができる。 In this way, by using Al contained in the flocculant as a replacement metal element when generating a p-type thermoelectric conversion material, a separate Al doping treatment is not required, and the flocculant is agglomerated by the flocculant. The silicon waste can be used as it is, and a thermoelectric conversion material can be obtained at low cost.
　以上、本発明を実施の形態に基づいて説明したが、本発明は上記の実施の形態に限定されるものではなく、本発明の範囲内で様々に変更および改変して実施することができる。 The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various changes and modifications can be made within the scope of the present invention.
（実施例）
　本実施例においては、放電プラズマ焼結装置（ＳＰＳシンテックス（株）製ＳＰＳ－５２０）を用いて焼結した。図３は、本実施例で用いた放電プラズマ焼結装置１０の基本構成図を示したものである。放電プラズマ焼結装置１０は、焼結ダイス９にセットされた試料を、上部パンチ７および下部パンチ８で加圧しながら、低電圧でパルス状大電流を投入し、火花放電現象により生じる放電プラズマを利用して焼結を行う。本実施例では、図４に示すように、焼結ダイスとして、グラファイト製の内径約２０mm、高さ４０mmのものを使用し、焼結ダイスと試料の剥離に厚さ０．２mmのカーボンシートを用いた。 (Example)
In this example, sintering was performed using a discharge plasma sintering apparatus (SPS-520 manufactured by SPS Shintex Co., Ltd.). FIG. 3 shows a basic configuration diagram of the discharge plasma sintering apparatus 10 used in this embodiment. The discharge plasma sintering apparatus 10 applies a pulsed large current at a low voltage while pressing the sample set on the sintering die 9 with the upper punch 7 and the lower punch 8, and generates a discharge plasma generated by a spark discharge phenomenon. Use it for sintering. In this example, as shown in FIG. 4, a graphite die having an inner diameter of about 20 mm and a height of 40 mm is used as the sintering die, and a carbon sheet having a thickness of 0.2 mm is used for peeling the sample from the sintering die. Using.
　本実施例では、シリコンウエハーの生産過程から回収されたシリコン廃棄物を、固体フラクションから液体フラクションを分離することなく、FeとSiの元素比が１：２となるように鉄成分と混合し、そのまま焼結ダイスに収容し、ダイスのパンチを通じて４０MPaで加圧した状態で、さらにパルス電流を通電して８００℃まで昇温して行い、ここで５分間保持したのち電流を切って冷却した。焼結の際の焼結室の真空度は約３Paであった。 In this example, the silicon waste recovered from the production process of the silicon wafer is mixed with the iron component so that the Fe to Si element ratio is 1: 2, without separating the liquid fraction from the solid fraction, It was accommodated in a sintered die as it was, pressurized with 40 MPa through a die punch, and further heated with a pulse current to 800 ° C., held for 5 minutes, then turned off and cooled. The degree of vacuum in the sintering chamber during sintering was about 3 Pa.
　以上の方法により生成された焼結体をＸ線回折したところ、β-FeSi２の結晶形態が存在することが確認され、シリコン廃棄物を鉄成分と混合し、SPS法によって高密度に焼結することで、シリコン廃棄物を熱電変換材料の材料として簡易かつ安価に利用できることがわかった。上記方法では、真空中で焼結を行ったが、窒素ガス、アルゴンガス、水素ガスあるいはこれらに混合ガス等の非酸化性雰囲気中で行うことができる。 As a result of X-ray diffraction of the sintered body produced by the above method, it was confirmed that a crystalline form of β-FeSi 2 was present, silicon waste was mixed with an iron component, and sintered at a high density by the SPS method. By doing so, it was found that silicon waste can be used simply and inexpensively as a material for thermoelectric conversion materials. In the above method, sintering is performed in a vacuum, but it can be performed in a non-oxidizing atmosphere such as nitrogen gas, argon gas, hydrogen gas, or a mixed gas thereof.
　本発明によれば、シリコン廃棄物における不純物を除去するとともに、酸化シリコンを還元することにより、シリコン廃棄物を簡易かつ安価に再利用して、高純度シリコンを生成することができ、太陽電池用シリコンなどとして有用である。また、本発明にかかる熱電変換材料は、放電プラズマ焼結法により、シリコンとFeの混合物に対して急加熱、短時間温度保持、および急冷を行うことで熱電変換材料が生成されると共に、シリコン廃棄物を利用することにより、簡易かつ安価に熱電変換材料を得ることができる。 According to the present invention, by removing impurities in silicon waste and reducing silicon oxide, it is possible to reuse silicon waste easily and inexpensively to produce high-purity silicon. Useful as silicon. In addition, the thermoelectric conversion material according to the present invention is produced by performing rapid heating, short-time temperature holding, and rapid cooling on a mixture of silicon and Fe by a discharge plasma sintering method. By using waste, a thermoelectric conversion material can be obtained simply and inexpensively.
１　特殊焼結電源（パルス電源）
２　制御装置
３　特殊加圧機構
４　水冷真空チャンバー
５　上部パンチ電極
６　下部パンチ電極
７　上部パンチ
８　下部パンチ
９　焼結ダイ
１０　放電プラズマ焼結装置
Ｐ　荷重 1 Special sintering power supply (pulse power supply)
2 Controller 3 Special pressurizing mechanism 4 Water-cooled vacuum chamber 5 Upper punch electrode 6 Lower punch electrode 7 Upper punch 8 Lower punch 9 Sintering die 10 Discharge plasma sintering apparatus P Load

Claims (22)

  1. 　シリコン廃棄物を放電プラズマ焼結法によって非酸化性雰囲気において高密度に焼結することにより生成されることを特徴とする高純度シリコン。 High purity silicon produced by sintering silicon waste at high density in a non-oxidizing atmosphere by a discharge plasma sintering method.
  2. 　約９００℃以上の焼結温度で前記シリコン廃棄物を焼結することを特徴とする請求項１に記載の高純度シリコン。 The high-purity silicon according to claim 1, wherein the silicon waste is sintered at a sintering temperature of about 900 ° C or higher.
  3. 　約９００℃の焼結温度で前記シリコン廃棄物を焼結することを特徴とする請求項１に記載の高純度シリコン。 The high-purity silicon according to claim 1, wherein the silicon waste is sintered at a sintering temperature of about 900 ° C.
  4. 　約１８００秒以上の保持時間で前記シリコン廃棄物を焼結することを特徴とする請求項１乃至３の何れかに記載の高純度シリコン。 The high-purity silicon according to any one of claims 1 to 3, wherein the silicon waste is sintered with a holding time of about 1800 seconds or more.
  5. 　前記放電プラズマ焼結法によって焼結された前記シリコン廃棄物を真空または非酸化性雰囲気において溶解することにより生成されることを特徴とする請求項１乃至４の何れかに記載の高純度シリコン。 The high-purity silicon according to any one of claims 1 to 4, wherein the high-purity silicon is produced by dissolving the silicon waste sintered by the discharge plasma sintering method in a vacuum or a non-oxidizing atmosphere.
  6. 　約１８００℃以上の溶解温度で前記シリコン廃棄物を溶解することを特徴とする請求項５に記載の高純度シリコン。 The high-purity silicon according to claim 5, wherein the silicon waste is melted at a melting temperature of about 1800 ° C or higher.
  7. 　前記シリコン廃棄物はＳｉＯおよびＳｉＣを含むことを特徴とする請求項５または６の何れかに記載の高純度シリコン。 The high-purity silicon according to any one of claims 5 and 6, wherein the silicon waste contains SiO and SiC.
  8. 　前記シリコン廃棄物にＣ系物質またはＣａ系物質を混合して溶解することを特徴とする請求項５乃至７の何れかに記載の高純度シリコン。 The high-purity silicon according to any one of claims 5 to 7, wherein a C-based material or a Ca-based material is mixed and dissolved in the silicon waste.
  9. 　溶解した前記シリコン廃棄物の表面に不活性ガスを吹き付けることを特徴とする請求項５乃至８の何れかに記載の高純度シリコン。 9. The high purity silicon according to claim 5, wherein an inert gas is sprayed on the surface of the dissolved silicon waste.
  10. 　溶解した前記シリコン廃棄物を冷却して固形化した後に、水素雰囲気において焼鈍処理を行うことを特徴とする請求項５乃至９の何れかに記載の高純度シリコン。 The high-purity silicon according to any one of claims 5 to 9, wherein after the dissolved silicon waste is cooled and solidified, an annealing treatment is performed in a hydrogen atmosphere.
  11. 　シリコン廃棄物をFe成分と混合し、放電プラズマ焼結法によって非酸化性雰囲気において焼結することにより生成されることを特徴とする熱電変換材料。 A thermoelectric conversion material produced by mixing silicon waste with an Fe component and sintering it in a non-oxidizing atmosphere by a discharge plasma sintering method.
  12. 　前記シリコン廃棄物は、放電プラズマ焼結法によって非酸化性雰囲気において焼結することにより、シリコンが高純度化されたシリコン廃棄物であることを特徴とする請求項１１に記載の熱電変換材料。 The thermoelectric conversion material according to claim 11, wherein the silicon waste is a silicon waste in which silicon is highly purified by sintering in a non-oxidizing atmosphere by a discharge plasma sintering method.
  13. 　前記シリコン廃棄物と前記Fe成分の混合物は、Feを含む凝集剤により、前記シリコン廃棄物を固液化した混合物であることを特徴とする請求項１１または１２に記載の熱電変換材料。 The thermoelectric conversion material according to claim 11 or 12, wherein the mixture of the silicon waste and the Fe component is a mixture obtained by solidifying the silicon waste with an aggregating agent containing Fe.
  14. 　前記Feを含む凝集剤は、塩化鉄、硫化鉄、もしくはこれらの組み合わせの何れかであることを特徴とする請求項１３に記載の熱電変換材料。 The thermoelectric conversion material according to claim 13, wherein the aggregating agent containing Fe is iron chloride, iron sulfide, or a combination thereof.
  15. 　前記シリコン廃棄物にAl成分を混合し、前記シリコン廃棄物と前記Al成分の混合物は、Alを含む凝集剤により、前記シリコン廃棄物を固液化した混合物であることを特徴とする請求項１１乃至１４の何れかに記載の熱電変換材料。 The Al component is mixed with the silicon waste, and the mixture of the silicon waste and the Al component is a mixture obtained by solidifying the silicon waste with an aggregating agent containing Al. The thermoelectric conversion material according to any one of 14.
  16. 　前記Alを含む凝集剤は、酸化アルミニウム、硫化アルミニウム、ポリ塩化アルミニウム、もしくはこれらの組み合わせの何れかであることを特徴とする請求項１５に記載の熱電変換材料。 The thermoelectric conversion material according to claim 15, wherein the flocculant containing Al is any one of aluminum oxide, aluminum sulfide, polyaluminum chloride, or a combination thereof.
  17. 　前記シリコン廃棄物は、シリコンウエハーの生産過程から生じるものであることを特徴とする請求項１１乃至１６の何れかに記載の熱電変換材料。 The thermoelectric conversion material according to any one of claims 11 to 16, wherein the silicon waste is generated from a production process of a silicon wafer.
  18. 　前記シリコン廃棄物は、洗浄工程により生じるものであって、主に純水とSiから成るシリコン廃棄物であることを特徴とする請求項１１乃至１７の何れかに記載の熱電変換材料。 The thermoelectric conversion material according to any one of claims 11 to 17, wherein the silicon waste is generated by a cleaning process and is silicon waste mainly composed of pure water and Si.
  19. 　前記シリコン廃棄物は、遠心分離、圧搾分離、沈降分離、浮上分離、もしくはこれらの組み合わせにより固液分離されたシリコン廃棄物であることを特徴とする請求項１１乃至１８の何れかに記載の熱電変換材料。 The thermoelectric generator according to any one of claims 11 to 18, wherein the silicon waste is silicon waste solid-liquid separated by centrifugation, squeezing separation, sedimentation separation, flotation separation, or a combination thereof. Conversion material.
  20. 　前記非酸化性雰囲気が、真空、窒素ガス、アルゴンガス、水素ガス、もしくはこれらの混合ガスの何れかであることを特徴とする請求項１１乃至１９の何れかに記載の熱電変換材料。 The thermoelectric conversion material according to any one of claims 11 to 19, wherein the non-oxidizing atmosphere is any one of vacuum, nitrogen gas, argon gas, hydrogen gas, or a mixed gas thereof.
  21. 　加圧圧力が１０～１００MPa、加熱・焼結温度が５００～２０００℃の範囲で前記焼結を行うことを特徴とする請求項１１乃至２０の何れかに記載の熱電変換材料。 The thermoelectric conversion material according to any one of claims 11 to 20, wherein the sintering is performed at a pressure of 10 to 100 MPa and a heating / sintering temperature of 500 to 2000 ° C.
  22. 　シリコン廃棄物をFe成分と混合し、放電プラズマ焼結法によって非酸化性雰囲気において焼結することにより生成することを特徴とする熱電変換材料生成方法。 A method for producing a thermoelectric conversion material, characterized in that silicon waste is mixed with an Fe component and sintered in a non-oxidizing atmosphere by a discharge plasma sintering method.
PCT/JP2009/005569 2008-11-12 2009-10-22 High grade silicon and thermoelectric conversion material WO2010055615A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2010537671A JPWO2010055615A1 (en) 2008-11-12 2009-10-22 High purity silicon and thermoelectric conversion materials

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2008-289413 2008-11-12
JP2008289413 2008-11-12

Publications (1)

Publication Number Publication Date
WO2010055615A1 true WO2010055615A1 (en) 2010-05-20

Family

ID=42169762

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2009/005569 WO2010055615A1 (en) 2008-11-12 2009-10-22 High grade silicon and thermoelectric conversion material

Country Status (2)

Country Link
JP (1) JPWO2010055615A1 (en)
WO (1) WO2010055615A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013007102A (en) * 2011-06-24 2013-01-10 Naoetsu Electronics Co Ltd Method of manufacturing iron silicon alloy
JP2014111519A (en) * 2012-11-12 2014-06-19 Panasonic Corp Silicon recycling system and method for the same
KR101448281B1 (en) 2011-10-24 2014-10-13 (주)태원시스켐 Silcon mould for alluminium alloy and preparation method thereof
DE102018200483B3 (en) * 2018-01-12 2019-03-21 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Thermoelectric material and method for producing a thermoelectric material and use of this material in a thermogenerator

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003286023A (en) * 2002-03-27 2003-10-07 Tdk Corp Production method of silicon sintered body and silicon sintered body
JP2004289065A (en) * 2003-03-25 2004-10-14 Nikko Materials Co Ltd Silicon sintered body and its manufacturing method
JP2008247670A (en) * 2007-03-30 2008-10-16 Hayashi Shokai:Kk Method of manufacturing high purity silicon

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003286023A (en) * 2002-03-27 2003-10-07 Tdk Corp Production method of silicon sintered body and silicon sintered body
JP2004289065A (en) * 2003-03-25 2004-10-14 Nikko Materials Co Ltd Silicon sintered body and its manufacturing method
JP2008247670A (en) * 2007-03-30 2008-10-16 Hayashi Shokai:Kk Method of manufacturing high purity silicon

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013007102A (en) * 2011-06-24 2013-01-10 Naoetsu Electronics Co Ltd Method of manufacturing iron silicon alloy
KR101448281B1 (en) 2011-10-24 2014-10-13 (주)태원시스켐 Silcon mould for alluminium alloy and preparation method thereof
JP2014111519A (en) * 2012-11-12 2014-06-19 Panasonic Corp Silicon recycling system and method for the same
DE102018200483B3 (en) * 2018-01-12 2019-03-21 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Thermoelectric material and method for producing a thermoelectric material and use of this material in a thermogenerator
WO2019137953A2 (en) 2018-01-12 2019-07-18 Leibniz-Institut Für Festkörper- Und Werkstoffforschung Dresden E.V. Thermoelectric material and process for producing a thermoelectric material
WO2019137953A3 (en) * 2018-01-12 2019-11-28 Leibniz-Institut Für Festkörper- Und Werkstoffforschung Dresden E.V. Thermoelectric material and process for producing a thermoelectric material

Also Published As

Publication number Publication date
JPWO2010055615A1 (en) 2012-04-12

Similar Documents

Publication Publication Date Title
Kong et al. An economical approach for the recycling of high-purity silicon from diamond-wire saw kerf slurry waste
De Sousa et al. Use of a thermal plasma process to recycle silicon kerf loss to solar-grade silicon feedstock
JP4523274B2 (en) High purity metallic silicon and its smelting method
JP3000109B2 (en) Manufacturing method of high purity silicon ingot
Hachichi et al. Silicon recovery from kerf slurry waste: a review of current status and perspective
Huang et al. A metallurgical route to upgrade silicon kerf derived from diamond-wire slicing process
Zhang et al. Recovery of silicon kerf waste from diamond wire sawing by two-step sintering and acid leaching method
Yang et al. A rapid thermal process for silicon recycle and refining from cutting kerf-loss slurry waste
KR20110127113A (en) Method and apparatus for refining metallurgical grade silicon to produce solar grade silicon
JP4465662B2 (en) Method for producing metal powder and method for producing target material
WO2010055615A1 (en) High grade silicon and thermoelectric conversion material
JPH10245216A (en) Production of silicon for solar cell
KR20110112223A (en) Method and system for manufacturing silicon and silicon carbide
JP4788925B2 (en) Method for purifying metallic silicon
Yin et al. Boron removal from molten silicon using sodium-based slags
JP4835867B2 (en) Silicon purification method
JPWO2008149985A1 (en) Solidification method of metallic silicon
JP2008303113A (en) Unidirectional coagulation method for silicon
JP2012236723A (en) Method for continuously refining silicon
JP2005255417A (en) Method for purifying silicon
JPH05262512A (en) Purification of silicon
JPH10182134A (en) Refining of silicon
US20210009431A1 (en) Silicon granules for the preparation of trichlorosilane and associated production method
JP5108354B2 (en) Manufacturing method of high purity silicon
KR20110004129A (en) Manufacturing method for silicon

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 09825869

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 2010537671

Country of ref document: JP

Kind code of ref document: A

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 09825869

Country of ref document: EP

Kind code of ref document: A1