CN117585679A - Method for preparing high-purity semi-insulating SiC powder by high-temperature solution method - Google Patents
Method for preparing high-purity semi-insulating SiC powder by high-temperature solution method Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 52
- 229910000676 Si alloy Inorganic materials 0.000 claims abstract description 110
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 79
- 239000002253 acid Substances 0.000 claims abstract description 75
- 150000002910 rare earth metals Chemical class 0.000 claims abstract description 75
- 239000013078 crystal Substances 0.000 claims abstract description 67
- 239000000956 alloy Substances 0.000 claims abstract description 42
- 238000005406 washing Methods 0.000 claims abstract description 37
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 31
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 28
- 239000010439 graphite Substances 0.000 claims abstract description 28
- 239000012141 concentrate Substances 0.000 claims abstract description 22
- 238000010438 heat treatment Methods 0.000 claims abstract description 19
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- 238000000227 grinding Methods 0.000 claims abstract description 7
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 7
- 238000011049 filling Methods 0.000 claims abstract description 3
- 229910052710 silicon Inorganic materials 0.000 claims description 40
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 37
- 239000010703 silicon Substances 0.000 claims description 37
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 24
- 229910052746 lanthanum Inorganic materials 0.000 claims description 23
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 23
- 229910052779 Neodymium Inorganic materials 0.000 claims description 22
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 claims description 22
- QZPSXPBJTPJTSZ-UHFFFAOYSA-N aqua regia Chemical compound Cl.O[N+]([O-])=O QZPSXPBJTPJTSZ-UHFFFAOYSA-N 0.000 claims description 14
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 13
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 claims description 13
- QWPPOHNGKGFGJK-UHFFFAOYSA-N hypochlorous acid Chemical compound ClO QWPPOHNGKGFGJK-UHFFFAOYSA-N 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 9
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 6
- 238000003723 Smelting Methods 0.000 claims description 6
- 238000005275 alloying Methods 0.000 claims description 6
- 229910017604 nitric acid Inorganic materials 0.000 claims description 6
- 229910052684 Cerium Inorganic materials 0.000 claims description 2
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 2
- 229910052691 Erbium Inorganic materials 0.000 claims description 2
- 229910052693 Europium Inorganic materials 0.000 claims description 2
- 229910052688 Gadolinium Inorganic materials 0.000 claims description 2
- 229910052689 Holmium Inorganic materials 0.000 claims description 2
- 229910052772 Samarium Inorganic materials 0.000 claims description 2
- 229910052771 Terbium Inorganic materials 0.000 claims description 2
- 229910052775 Thulium Inorganic materials 0.000 claims description 2
- 229910052769 Ytterbium Inorganic materials 0.000 claims description 2
- 229910002065 alloy metal Inorganic materials 0.000 claims description 2
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 2
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 claims description 2
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 claims description 2
- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 claims description 2
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 claims description 2
- KJZYNXUDTRRSPN-UHFFFAOYSA-N holmium atom Chemical compound [Ho] KJZYNXUDTRRSPN-UHFFFAOYSA-N 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 claims description 2
- 229910052706 scandium Inorganic materials 0.000 claims description 2
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 claims description 2
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 claims description 2
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 claims description 2
- 229910052727 yttrium Inorganic materials 0.000 claims description 2
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 2
- 238000007711 solidification Methods 0.000 claims 1
- 230000008023 solidification Effects 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 6
- 238000002360 preparation method Methods 0.000 abstract description 4
- 229910010271 silicon carbide Inorganic materials 0.000 description 122
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 50
- 239000002994 raw material Substances 0.000 description 14
- 239000012535 impurity Substances 0.000 description 7
- 238000010532 solid phase synthesis reaction Methods 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 5
- 238000001514 detection method Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 239000007791 liquid phase Substances 0.000 description 4
- 238000011068 loading method Methods 0.000 description 4
- 238000004064 recycling Methods 0.000 description 4
- 229910052720 vanadium Inorganic materials 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910010293 ceramic material Inorganic materials 0.000 description 3
- 238000001036 glow-discharge mass spectrometry Methods 0.000 description 3
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- 239000011863 silicon-based powder Substances 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
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- 238000005229 chemical vapour deposition Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 238000003980 solgel method Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000001308 synthesis method Methods 0.000 description 2
- 239000012808 vapor phase Substances 0.000 description 2
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 1
- -1 SiC saturated silicon Chemical class 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- MWGJWEQXHPHZLV-UHFFFAOYSA-N [Si].[Nd] Chemical compound [Si].[Nd] MWGJWEQXHPHZLV-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
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- 239000002019 doping agent Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000003758 nuclear fuel Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/90—Carbides
- C01B32/914—Carbides of single elements
- C01B32/956—Silicon carbide
- C01B32/963—Preparation from compounds containing silicon
- C01B32/984—Preparation from elemental silicon
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Abstract
The invention relates to a method for preparing high-purity semi-insulating SiC powder by a high-temperature solution method, and belongs to the technical field of material preparation. The method comprises the steps of filling a rare earth-containing silicon alloy material into a graphite container, and placing the graphite container in a non-constant-temperature heating area of a heating furnace; in Ar or Ar-H 2 Heating a graphite container in the atmosphere to completely melt the silicon alloy material containing rare earth to obtain a silicon alloy melt saturated with SiC; the surface temperature of the silicon alloy melt is 1650 ℃ and kept for more than 1h, and 3C-SiC crystals are separated out from the low-temperature end of the silicon alloy melt under the action of a temperature gradient; 3C-SiC crystals precipitated under the action of electromagnetic force and/or temperature gradient are gathered and grown at the low temperature end, and finally residual silicon alloy melt and 3C-SiC crystal enrichment are respectively obtained at the high temperature end and the low temperature end of the silicon alloy melt; after cooling and solidifying, separating the 3C-SiC crystal concentrate from the residual silicon alloy, and grinding the 3C-SiC crystal concentrate to obtain 3C-SiC crystal concentrate powder; and carrying out acid washing on the 3C-SiC crystal enriched powder for three times to obtain high-purity semi-insulating 3C-SiC powder.
Description
Technical Field
The invention relates to a method for preparing high-purity semi-insulating SiC powder by a high-temperature solution method, and belongs to the technical field of material preparation.
Background
Silicon carbide (SiC) is used as an advanced structure ceramic material and a third generation wide forbidden band semiconductor material, and by virtue of the excellent high-temperature mechanical strength (no deformation at 2300 ℃), high hardness (Brinell hardness of more than 9), high thermal conductivity (thermal conductivity of 165W/M.K), small thermal expansion coefficient, high breakdown field strength, high electron saturation drift rate, strong radiation resistance, acid and alkali corrosion resistance and other performances, the silicon carbide (SiC) can be applied to the traditional industrial fields of high-temperature kiln furniture, combustion nozzles, heat exchangers, sealing rings, sliding bearings and the like, and can also be used as a bulletproof armor material, a space optical part, a semiconductor material SiC monocrystal and a nuclear fuel cladding material. The SiC powder is a raw material for preparing compact ceramic materials and SiC single crystals, the purity of the SiC powder is an important factor influencing the quality of the SiC ceramic materials, and the purity of the SiC powder is required to be more than 99.995 percent especially when preparing semi-insulating SiC single crystals by a physical vapor transport method (PVT method).
The synthesis methods of the high-purity SiC powder are various and can be divided into: (1) solid phase methods such as carbothermic reduction (Acheson process), synthesis. The carbothermal reduction method uses high-purity graphite powder as C source and SiO 2 Preparing SiC powder by reacting for a long time (about 1 week) at 2200-2400 ℃ under negative pressure as Si source, wherein free C and SiO exist in the product 2 Further removal is required. The synthesis method is to directly react and synthesize SiC powder by adopting C powder and Si powder at 2000 ℃, and purify the synthesized SiC powder to prepare SiC powder with the purity of 99.999 percent. (2) The liquid phase method is sol-gel method and polymer decomposition method. In the prior art, only a sol-gel method can synthesize high-purity SiC powder, and the technology takes industrial silica sol and water-soluble phenolic resin as raw materials, and carries out carbothermal reduction reaction at high temperature to obtain the SiC powder with the nano-grade purity of 99.95 percent. (3) The vapor phase method includes a vapor phase reaction deposition method (CVD method) and a plasma method. The CVD method is to use SiH 4 C as a silicon source 2 H 2 As a carbon source, ar gas was used as a carrier gas to synthesize a catalyst having a particle size of 5 to 20nm and a purity of 99.999% of high-purity SiC powder. The plasma method is to introduce reaction gas into a plasma container excited by a radio frequency power supply, and the gas reacts with each other under the collision of high-speed electrons to obtain high-purity SiC powder with the particle size of 4-6 nm.
The solid phase method is adopted to synthesize the SiC powder with high purity, simple process and low raw material cost, and is suitable for industrial mass production. However, in order to ensure that raw materials Si powder and C powder can fully react when synthesizing SiC powder, extremely fine granularity is required to be uniformly mixed, but the specific surface area of the raw materials is increased, and a large amount of N element in air is extremely easy to adsorb, so that the content of N element in the synthesized SiC powder is higher (the N content is less than 500 ppm), and N is a typical N-type doping agent in SiC single crystal, therefore, the SiC single crystal grown by adopting the SiC powder with high N content cannot meet the use requirement of a semi-insulating single crystal substrate; in addition, the Si/C ratio of the raw materials is not easy to control, so that free Si or C is mixed in the synthesized SiC, and therefore, the problem that the solid phase method is difficult to synthesize the SiC powder is how to reduce the content of N element in the SiC powder, and the C and Si which are not completely reacted in the SiC powder are difficult to remove later. The liquid phase method is adopted to synthesize the SiC powder, so that the cost of raw materials is high, the synthesis process is complex, and the method is not suitable for industrial production. The gas phase method is adopted to synthesize SiC powder, so that the purity requirements on an organic gas source and graphite pieces are high, the raw material cost is high, the synthesized powder is nano-scale ultrafine powder, the nano-scale ultrafine powder is not easy to collect, the synthesis rate is low, and the mass production is not possible.
Disclosure of Invention
Aiming at the technical problem that high-purity SiC powder is difficult to prepare, the invention provides a method for preparing high-purity semi-insulating SiC powder by a high-temperature solution method, which adopts a low-purity rare earth-containing silicon alloy material and a low-purity graphite container as Si sources and C sources for synthesizing high-purity 3C-SiC powder, wherein the rare earth-containing silicon alloy material and the graphite container are blocks, so that the problems of high cost and incomplete reaction of C and Si impurities caused when the high-purity Si powder and the C powder are adopted as raw materials in the traditional method for synthesizing the SiC powder are avoided.
A method for preparing high-purity semi-insulating SiC powder by a high-temperature solution method comprises the following specific steps:
(1) Alloying and smelting silicon or silicon-based alloy and rare earth metal to obtain a silicon alloy material containing rare earth, filling the silicon alloy material containing rare earth into a graphite container, and then placing the graphite container in a non-constant-temperature heating area of a heating furnace; the total mass fraction of rare earth and silicon in the rare earth-containing silicon alloy material is not higher than 99.9%, the molar content of rare earth elements in the rare earth-containing silicon alloy material is 30-38%, and the purity of the graphite container is not higher than 99.94%;
(2) In Ar or Ar-H 2 Heating a graphite container in an atmosphere to completely melt a silicon alloy material containing rare earth, obtaining a silicon alloy melt saturated with SiC, keeping the surface temperature of the silicon alloy melt at 1650 ℃ for more than 1h, separating out 3C-SiC crystals at the low temperature end of the silicon alloy melt under the action of a temperature gradient, gathering and growing the separated 3C-SiC crystals at the low temperature end under the action of electromagnetic force and/or the temperature gradient, and finally obtaining residual silicon alloy melt and 3C-SiC crystal enrichment at the high temperature and the low temperature end of the silicon alloy melt respectively;
(3) After cooling and solidifying, separating the 3C-SiC crystal concentrate from the residual silicon alloy, and grinding the 3C-SiC crystal concentrate to obtain 3C-SiC crystal concentrate powder with the granularity not more than 75 mu m; adding silicon into the residual silicon alloy to enable the molar ratio of the silicon to the rare earth in the residual silicon alloy to be equal to the molar ratio of the silicon to the rare earth in the silicon alloy containing the rare earth in the step (1), and then returning to the step (1) to be added into the silicon alloy material containing the rare earth;
(4) The 3C-SiC crystal enriched powder is sequentially subjected to first acid washing, second acid washing and third acid washing to obtain high-purity semi-insulating 3C-SiC powder.
The rare earth in the silicon alloy material containing rare earth in the step (1) is one or more of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium and ytterbium.
The temperature gradient of the non-constant temperature heating area in the step (1) is 10-30K/cm.
The step (1) Ar-H 2 Middle H 2 The volume content of (2) is 5-10%.
And (3) completely melting the rare earth-containing silicon alloy material in the step (2) to form a rare earth-containing silicon alloy melt, and dissolving carbon elements of a graphite container as solutes in the rare earth-containing silicon alloy melt to form a high-temperature solution, namely a SiC saturated silicon alloy melt.
The acid liquor of the first acid washing in the step (4) is hydrochloric acid or aqua regia, and the acid liquor of the second acid washing is HF-HNO 3 Mixed acid, the acid liquor of the third acid washing is aqua regia or HClO 4 -HNO 3 And (5) mixing acid.
The concentration of the hydrochloric acid is 11.6-12.3 mol/L, the volume ratio of the concentrated nitric acid to the concentrated hydrochloric acid in the aqua regia is 1:3, and the HF-HNO is used for treating the sewage 3 The concentration of HF in the mixed acid is 11.2 mol/L and HNO 3 The concentration is 7.2-7.6 mol/L; HClO 4 -HNO 3 HClO in mixed acid 4 The concentration is 6-6.2 mol/L, HNO 3 The concentration is 7.2-7.6 mol/L.
The rare earth element content in the high-purity semi-insulating 3C-SiC powder in the step (4) is less than 1ppm, and the mass content of the 3C-SiC is not less than 99.999%.
The beneficial effects of the invention are as follows:
(1) Compared with the existing solid phase method for reaction and preparation of SiC powder, the invention adopts liquid phase reaction, and utilizes segregation behavior of impurities at a solid-liquid interface to lead impurities in raw materials to stay in liquid phase melt instead of solid phase SiC crystal, thus finally preparing high-purity semi-insulating 3C-SiC crystal; the method avoids the uneven or incomplete reaction of the raw material C, siO by the solid phase method 2 Or Si remains in the prepared SiC powder, and the preparation temperature of the invention is 1650 ℃ lower than that of the traditional solid phase method (higher than 2000 ℃);
(2) The raw materials of the invention adopt low-purity rare earth-containing silicon alloy and a low-purity graphite crucible (the purity of the raw materials is lower than that of the prepared SiC crystal), and the 3C-SiC crystal is enriched at the low temperature end of the silicon alloy melt by utilizing the action of electromagnetic force or temperature gradient to obtain a 3C-SiC crystal enriched substance, and the residual silicon alloy melt remained at the upper end of the 3C-SiC crystal enriched substance can be recycled, thereby achieving the purpose of recovering rare earth;
(3) The solid phase method is difficult to prepare 3C-SiC crystals (because 3C-SiC is converted into 4H-SiC or 6H-SiC at the temperature of more than 1800 ℃) due to high reaction temperature, and the invention can easily obtain high-purity 3C-SiC powder with the rare earth content of less than 1ppmw and the purity of more than 99.999 percent, thereby providing a high-quality raw material for growing semi-insulating SiC single crystals by the PVT method;
(4) The method for preparing the high-purity semi-insulating 3C-SiC crystal has the characteristics of low cost, low energy consumption and high efficiency.
Drawings
FIG. 1 is a sample XRD diffraction pattern of the 3C-SiC powder of example 1;
FIG. 2 is a sample XRD diffraction pattern of the 3C-SiC powder of example 2;
FIG. 3 is a sample XRD diffraction pattern of the 3C-SiC powder of example 3;
FIG. 4 is a sample XRD diffraction pattern of the 3C-SiC powder of example 4.
Detailed Description
The invention will be described in further detail with reference to specific embodiments, but the scope of the invention is not limited to the description.
Example 1: a method for preparing high-purity semi-insulating SiC powder by a high-temperature solution method comprises the following specific steps:
(1) Alloying and smelting silicon and rare earth neodymium to obtain a silicon alloy material containing rare earth neodymium, loading the silicon alloy material containing rare earth neodymium (Nd) (the total mass fraction of the rare earth neodymium and the silicon is 99.9%) into a graphite crucible (the purity is 99.94%), and then placing the graphite crucible in a non-constant temperature heating area of an induction furnace with a temperature gradient of 30K/cm; the molar content of neodymium (Nd) in the silicon alloy material containing rare earth neodymium (Nd) is 38%, and the molar ratio of silicon to neodymium is 1.6:1;
(2) Heating a graphite crucible in Ar atmosphere to completely melt a silicon alloy material containing rare earth neodymium (Nd) to obtain a silicon alloy melt saturated with SiC, keeping the surface temperature of the silicon alloy melt at 1650 ℃ and preserving heat for 1h, separating out 3C-SiC crystals at the low temperature end of the silicon alloy melt under the action of temperature gradient, continuously gathering and growing the 3C-SiC crystals at the low temperature end under the action of electromagnetic force and temperature gradient, and finally obtaining residual silicon alloy melt and 3C-SiC crystal concentrates at the high and low temperature ends of the silicon alloy melt respectively;
(3) After cooling and solidifying, separating the 3C-SiC crystal concentrate from the residual silicon alloy, and grinding the 3C-SiC crystal concentrate to 75 mu m of granularity to obtain 3C-SiC crystal concentrate powder; adding silicon into the residual silicon alloy to enable the molar ratio of the silicon to the neodymium in the residual silicon alloy to be equal to 1.6:1 of the molar ratio of the silicon to the neodymium in the rare earth-containing silicon alloy in the step (1), and returning to the step (1) to be added into the rare earth-containing neodymium silicon alloy material, so that the recycling of the residual silicon alloy can be realized;
(4) The 3C-SiC crystal enriched powder is sequentially subjected to first acid washing, second acid washing and third acid washing to obtain high-purity semi-insulating 3C-SiC powder; the acid liquor for the first acid washing is hydrochloric acid with the molar concentration of 12.3 mol/L; the acid liquid of the second acid washing is HF-HNO 3 Mixed acid, HF-HNO 3 The concentration of HF in the mixed acid is 11.2 mol/L and HNO 3 The concentration is 7.6 mol/L; the acid liquor for the third acid washing is aqua regia, and the volume ratio of the concentrated nitric acid to the concentrated hydrochloric acid in the aqua regia is 1:3;
the XRD diffraction pattern of the powder sample of the 3C-SiC powder of the embodiment is shown in figure 1, and the crystal form of the powder sample is 3C-SiC as can be seen from figure 1;
the Nd content of the high-purity semi-insulating 3C-SiC powder is 0.8 ppmw, and the purity is 99.9996%; specifically, the impurity and the content of the high-purity semi-insulating 3C-SiC powder are respectively F:1.2 ppmw, mg:0.31 ppmw, P:0.56 ppmw, ca:0.08 ppmw, ti:0.25 ppmw, fe:0.27 ppmw, mn:0.07 ppmw, ni:0.28 ppmw, nd:0.8 ppmw, B, V, cr and Co content were below the detection limit of GD-MS.
Example 2: a method for preparing high-purity semi-insulating SiC powder by a high-temperature solution method comprises the following specific steps:
(1) Alloying and smelting a silicon-based alloy and rare earth praseodymium (Pr) to obtain a silicon alloy material containing the rare earth praseodymium (Pr), loading the silicon alloy material containing the rare earth praseodymium (Pr) (the total mass fraction of the rare earth praseodymium and silicon is 99.9%) into a graphite crucible (the purity is 99.94%), and then placing the graphite crucible in a non-constant temperature heating area of an induction furnace with a temperature gradient of 22K/cm; the mol content of praseodymium (Pr) in the silicon alloy material containing the rare earth praseodymium (Pr) is 30%, and the mol ratio of silicon to praseodymium is 2.3:1;
(2) Under Ar atmosphere, heating a graphite crucible to enable a silicon alloy material containing rare earth praseodymium (Pr) to be completely melted, obtaining a silicon alloy melt saturated with SiC, keeping the surface temperature of the silicon alloy melt at 1650 ℃ and preserving heat for 2 hours, under the action of a temperature gradient, separating out 3C-SiC crystals at the low temperature end of the silicon alloy melt, continuously gathering and growing the 3C-SiC crystals at the low temperature end under the action of electromagnetic force, and finally obtaining residual silicon alloy melt and 3C-SiC crystal enrichment at the high temperature and the low temperature end of the silicon alloy melt respectively;
(3) After cooling and solidifying, separating the 3C-SiC crystal concentrate from the residual silicon alloy, and grinding the 3C-SiC crystal concentrate to the granularity of 61 mu m to obtain 3C-SiC crystal concentrate powder; adding silicon into the residual silicon alloy to enable the molar ratio of the silicon to the rare earth praseodymium in the residual silicon alloy to be equal to 2.3:1 of the molar ratio of the silicon to the rare earth praseodymium in the rare earth-containing silicon alloy in the step (1), and then returning to the step (1) to add the mixture into the rare earth praseodymium-containing silicon alloy material, so that the recycling of the residual silicon alloy can be realized;
(4) The 3C-SiC crystal enriched powder is sequentially subjected to first acid washing, second acid washing and third acid washing to obtain high-purity semi-insulating 3C-SiC powder; the acid liquor for the first acid washing is hydrochloric acid with the molar concentration of 11.6 mol/L; the acid liquid of the second acid washing is HF-HNO 3 Mixed acid, HF-HNO 3 The concentration of HF in the mixed acid is 11.2 mol/L and HNO 3 The concentration is 7.2 mol/L; the acid liquid of the third acid washing is HClO 4 -HNO 3 Mixed acid, HClO 4 -HNO 3 HClO in mixed acid 4 The concentration is 6.2 mol/L, HNO 3 The concentration is 7.2 mol/L;
the XRD diffraction pattern of the powder sample of the 3C-SiC powder of the embodiment is shown in figure 2, and the crystal form of the powder sample is 3C-SiC as can be seen from figure 2;
the Pr content of the high-purity semi-insulating 3C-SiC powder is 0.31ppmw, and the purity is 99.9994%; specifically, the impurity and the content of the high-purity semi-insulating 3C-SiC powder are respectively F:1.1 ppmw, mg:0.09 ppmw, P:0.71 ppmw, ca:0.1 ppmw, ti:1.7 ppmw, fe:0.8 ppmw, mn:0.2 ppmw, ni:0.27 ppmw, pr: the B, V, cr and Co contents were below the detection limit of GD-MS, 0.31 ppmw.
Example 3: a method for preparing high-purity semi-insulating SiC powder by a high-temperature solution method comprises the following specific steps:
(1) Alloying and smelting silicon and rare earth lanthanum (La) to obtain a silicon alloy material containing the rare earth lanthanum (La), loading the silicon alloy material containing the rare earth lanthanum (La) (the total mass fraction of the rare earth lanthanum and the silicon is 99.9%) into a graphite crucible (the purity is 99.94%), and then placing the graphite crucible in a non-constant-temperature heating area of a resistance furnace with a temperature gradient of 10K/cm; the molar content of lanthanum (La) in the silicon alloy material containing rare earth lanthanum (La) is 35%, and the molar ratio of silicon to lanthanum is 1.8:1;
(2) In Ar-5vol.% H 2 Heating a graphite crucible to completely melt a silicon alloy material containing rare earth lanthanum (La) to obtain a silicon alloy melt saturated with SiC, keeping the surface temperature of the silicon alloy melt at 1650 ℃ and preserving heat for 3 hours, separating out 3C-SiC crystals at the low temperature end of the silicon alloy melt under the action of a temperature gradient, continuously gathering and growing the 3C-SiC crystals at the low temperature end under the action of the temperature gradient, and finally obtaining residual silicon alloy melt and 3C-SiC crystal enrichment at the high and low temperature ends of the silicon alloy melt respectively;
(3) After cooling and solidifying, separating the 3C-SiC crystal concentrate from the residual silicon alloy, and grinding the 3C-SiC crystal concentrate to 75 mu m of granularity to obtain 3C-SiC crystal concentrate powder; adding silicon into the residual silicon alloy to enable the molar ratio of the silicon to the rare earth lanthanum in the residual silicon alloy to be equal to 1.8:1 of the molar ratio of the silicon to the rare earth lanthanum in the rare earth-containing silicon alloy in the step (1), and then returning to the step (1) to add the silicon alloy into the rare earth lanthanum-containing silicon alloy material to realize recycling of the residual silicon alloy;
(4) The 3C-SiC crystal enriched powder is sequentially subjected to first acid washing, second acid washing and third acid washing to obtain high-purity semi-insulating 3C-SiC powder; the acid liquor for the first acid washing is aqua regia, and the volume ratio of the concentrated nitric acid to the concentrated hydrochloric acid in the aqua regia is 1:3; the acid liquid of the second acid washing is HF-HNO 3 Mixed acid, HF-HNO 3 The concentration of HF in the mixed acid is 11.2 mol/L and HNO 3 The concentration is 7.6 mol/L; the acid liquid of the third acid washing is HClO 4 -HNO 3 Mixed acid, HClO 4 -HNO 3 HClO in mixed acid 4 The concentration is 6 mol/L, HNO 3 The concentration is 7.6 mol/L;
the XRD diffraction pattern of the sample of the powder of the 3C-SiC powder of the embodiment is shown in figure 3, and the crystal form of the powder is 3C-SiC as shown in figure 3;
the La content of the high-purity semi-insulating 3C-SiC powder is 0.6 ppmw, and the purity is 99.9996%; specifically, the impurity and the content of the high-purity semi-insulating 3C-SiC powder are respectively F:1.3 ppmw, mg:0.09 ppmw, P:0.8 ppmw, ca:0.08 ppmw, ti:0.16 ppmw, fe:0.27 ppmw, mn:0.07 ppmw, ni:0.31 ppmw, la:0.6 ppmw, B, V, cr and Co content were all below the detection limit of GD-MS.
Example 4: a method for preparing high-purity semi-insulating SiC powder by a high-temperature solution method comprises the following specific steps:
(1) Alloying and smelting silicon, rare earth lanthanum (La) and neodymium (Nd) to obtain a silicon alloy material containing the rare earth lanthanum (La) and neodymium (Nd), loading the silicon alloy material containing the rare earth lanthanum (La) and neodymium (Nd) (the total mass fraction of the rare earth and the silicon is 99.9%) into a graphite crucible (99.94%), and then placing the graphite crucible in a non-constant-temperature heating area of an induction furnace with a temperature gradient of 25K/cm; the molar content of lanthanum (La) in the silicon alloy material containing rare earth lanthanum (La) and neodymium (Nd) is 20 percent, the molar content of neodymium (Nd) is 10 percent, and the molar ratio of silicon to rare earth (total molar amount of lanthanum and neodymium) is 2.3:1;
(2) In Ar-10vol.% H 2 Under the atmosphere, heating a graphite crucible to completely melt a silicon alloy material containing rare earth lanthanum (La) and neodymium (Nd) to obtain a silicon alloy melt saturated with SiC, keeping the surface temperature of the silicon alloy melt at 1650 ℃ and preserving heat for 2 hours, separating out 3C-SiC crystals at the low temperature end of the silicon alloy melt under the action of a temperature gradient, continuously gathering and growing the 3C-SiC crystals at the low temperature end under the action of electromagnetic force, and finally obtaining residual silicon alloy melt and 3C-SiC crystal enrichment at the high temperature and the low temperature end of the silicon alloy melt respectively;
(3) After cooling and solidifying, separating the 3C-SiC crystal concentrate from the residual silicon alloy, and grinding the 3C-SiC crystal concentrate to the granularity of 25 mu m to obtain 3C-SiC crystal concentrate powder; adding silicon into the residual silicon alloy to enable the molar ratio of the silicon to the rare earth (total molar quantity of lanthanum and neodymium) in the residual silicon alloy to be equal to the molar ratio of the silicon to the rare earth (total molar quantity of lanthanum and neodymium) in the silicon alloy containing the rare earth in the step (1) to be 2.3:1, and then returning to the step (1) to be added into the silicon alloy material containing the rare earth, so that the recycling of the residual silicon alloy can be realized;
(4) The 3C-SiC crystal enriched powder is sequentially subjected to first acid washing, second acid washing and third acid washing to obtain high-purity semi-insulating 3C-SiC powder; the acid liquor for the first acid washing is aqua regia, and the volume ratio of the concentrated nitric acid to the concentrated hydrochloric acid in the aqua regia is 1:3; the acid liquid of the second acid washing is HF-HNO 3 Mixed acid, HF-HNO 3 The concentration of HF in the mixed acid is 11.2 mol/L and HNO 3 The concentration is 7.6 mol/L; the acid liquor for the third acid washing is aqua regia, and the volume ratio of the concentrated nitric acid to the concentrated hydrochloric acid in the aqua regia is 1:3;
the XRD diffraction pattern of the sample of the powder of the 3C-SiC powder of the embodiment is shown in figure 4, and the crystal form of the powder is 3C-SiC as shown in figure 4;
the high-purity semi-insulating 3C-SiC powder of the embodiment has lanthanum (La) content of 0.53ppmw, neodymium (Nd) content of 0.37 ppmw and purity of 99.9996%; specifically, the impurity and the content of the high-purity semi-insulating 3C-SiC powder are respectively F:0.96 ppmw, P:0.56 ppmw, ca:0.06 ppmw, ti:0.16 ppmw, fe:0.22 ppmw, mn:0.17 ppmw, ni:0.32 ppmw, la:0.53 ppmw, nd:0.37 ppmw; mg, B, V, cr and Co content are below detection limits.
While the specific embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes may be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.
Claims (6)
1. A method for preparing high-purity semi-insulating SiC powder by a high-temperature solution method is characterized by comprising the following specific steps:
(1) Alloying and smelting silicon or silicon-based alloy and rare earth metal to obtain a silicon alloy material containing rare earth, filling the silicon alloy material containing rare earth into a graphite container, and then placing the graphite container in a non-constant-temperature heating area of a heating furnace; the total mass fraction of rare earth and silicon in the rare earth-containing silicon alloy material is not higher than 99.9%, the molar content of rare earth elements in the rare earth-containing silicon alloy material is 30-38%, and the purity of the graphite container is not higher than 99.94%;
(2) In Ar or Ar-H 2 Heating a graphite container in the atmosphere to completely melt a silicon alloy material containing rare earth to obtain a silicon alloy melt saturated with SiC, and keeping the surface temperature of the silicon alloy melt at 1650 ℃ for more than 1 h; under the action of temperature gradient, 3C-SiC crystals are separated out from the low-temperature end of the silicon alloy melt, under the action of electromagnetic force and/or temperature gradient, the separated 3C-SiC crystals are gathered and grown up at the low-temperature end, and finally residual silicon alloy melt and 3C-SiC crystal enrichment are respectively obtained at the high-temperature end and the low-temperature end of the silicon alloy melt;
(3) After cooling and solidification, separating the 3C-SiC crystal concentrate from the residual silicon alloy; grinding the 3C-SiC crystal concentrate to obtain 3C-SiC crystal concentrate powder with granularity not more than 75 mu m; adding silicon into the residual silicon alloy to enable the molar ratio of the silicon to the rare earth in the residual silicon alloy to be equal to the molar ratio of the silicon to the rare earth in the silicon alloy containing the rare earth in the step (1), and then returning to the step (1) to be added into the silicon alloy material containing the rare earth;
(4) The 3C-SiC crystal enriched powder is sequentially subjected to first acid washing, second acid washing and third acid washing to obtain high-purity semi-insulating 3C-SiC powder.
2. The method for preparing high-purity semi-insulating SiC powder by the high-temperature solution method according to claim 1, characterized in that: the rare earth in the silicon alloy material containing rare earth in the step (1) is one or more of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium and ytterbium.
3. The method for preparing high-purity semi-insulating SiC powder by the high-temperature solution method according to claim 1, characterized in that: the temperature gradient of the non-constant temperature heating area in the step (1) is 10-30K/cm.
4. The method for preparing high-purity semi-insulating SiC powder by the high-temperature solution method according to claim 1, characterized in that: step (4) first acidThe acid liquid for washing is hydrochloric acid or aqua regia, and the acid liquid for the second acid washing is HF-HNO 3 Mixed acid, the acid liquor of the third acid washing is aqua regia or HClO 4 -HNO 3 And (5) mixing acid.
5. The method for preparing high-purity semi-insulating SiC powder by the high-temperature solution method according to claim 4, wherein the method comprises the following steps: the concentration of hydrochloric acid is 11.6-12.3 mol/L; the volume ratio of the concentrated nitric acid to the concentrated hydrochloric acid in the aqua regia is 1:3; HF-HNO 3 The concentration of HF in the mixed acid is 11.2 mol/L and HNO 3 The concentration is 7.2-7.6 mol/L; HClO 4 -HNO 3 HClO in mixed acid 4 The concentration is 6-6.2 mol/L, HNO 3 The concentration is 7.2-7.6 mol/L.
6. The method for preparing high-purity semi-insulating SiC powder by the high-temperature solution method according to claim 1, characterized in that: the rare earth element content in the high-purity semi-insulating 3C-SiC powder in the step (4) is less than 1ppm, and the mass content of the 3C-SiC is not less than 99.999%.
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