CN103613381B - Preparation method of N-type gadolinium-doped strontium titanate oxide pyroelectric ceramic - Google Patents
Preparation method of N-type gadolinium-doped strontium titanate oxide pyroelectric ceramic Download PDFInfo
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- CN103613381B CN103613381B CN201310539162.8A CN201310539162A CN103613381B CN 103613381 B CN103613381 B CN 103613381B CN 201310539162 A CN201310539162 A CN 201310539162A CN 103613381 B CN103613381 B CN 103613381B
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Abstract
The invention discloses a preparation method of N-type gadolinium-doped strontium titanate oxide pyroelectric ceramic, which comprises the following steps: according to stoichiometric ratio of a general formula (Sr1-xGdx)TiO3 (x=0.05-0.1), taking butyl titanate (Ti(OC4H9)4) as a titanium source, taking absolute ethyl alcohol and glycol as a solvent and a dispersant, mixing with strontium nitrate/gadolinium salt liquid under the condition that citric acid is taken as a complexing agent, a sol-gel method is employed to prepare the single-phase nano forerunner powder; performing one-step reduction on the forerunner powder in a reducing atmosphere, putting the grinded powder in a graphite die, using discharge plasma for sintering to a block material, wherein the sintering temperature is 1200-1400 DEG C, and insulating for 1-30 minutes. Compared with a traditional solid phase sintering hot pressing moulding method, and the preparation method has the advantages of short reaction time, low energy consumption, high production efficiency, high products density, small crystal grain size and the like, and is suitable for preparing high temperature oxide thermoelectricity ceramic.
Description
Technical field
The invention belongs to meticulous ceramic material field, relate to a kind of preparation of sol-gel precursor powder of using, after a step reduction, use discharge plasma sintering (SPS) technology fast preparation have that density is high, grain-size is little, the method for the N-type of excellent performance (electronic conduction) gadolinium strontium titanate doping thermoelectric ceramics.
Background technology
Energy scarcity is the significant challenge that the world today faces.For the thermo-electric device of thermo-electric generation, can realize the mutual conversion of heat energy and electric energy, and not need any drive disk assembly, without greenhouse gas emission, be a kind of typical green energy resource technology.The efficiency of thermo-electric device is by manufacturing the P type (hole conduction) of this device and the decision of the pyroelectric material performance of N-type (electronic conduction), and therefore, the thermoelectric material that preparation has excellent properties is the focus of current research.Thermoelectric material is a kind of material that heat energy and electric energy can be changed mutually, and its efficiency of conversion is generally used non-dimensional parameter thermoelectric figure of merit ZT(ZT=S
2σ T/ κ, S is thermoelectric force, and σ is specific conductivity, and T is absolute temperature, κ is thermal conductivity) represent.Strontium titanate (SrTiO
3) be that one has typical uhligite (ABO
3) transition metal oxide of structure, higher energy gap (3.2eV), the dark doping that can be easy to realize Sr position or Ti position atom is replaced, and shows unique optics, catalysis, ionic conductivity and thermoelectric property.Utilize rare earth element to realize to strontium titanate the degeneracy semiconductor metal oxide that N-type heavy doping is prepared, there is good chemistry and thermostability, Constitution Elements is nontoxic, and low price and earth deposit are abundant, are suitable for high temperature electricity generation material (temperature can reach 1000K).The strontium titanate film of Nb doping is that hitherto reported has one of the N-shaped oxide pyroelectric material of maximum ZT (ZT=0.37, T=1000K), has fully demonstrated potential advantages and the researching value of Strontium carbonate powder as N-type oxide high-temperature thermoelectric material.But because the preparation cost of film is higher, can not meet actual demand.How to prepare low thermal conductance, high-performance thermoelectric ceramics bulk, the difficult point that becomes a reality and face.
The method of preparing at present strontium titanate doping thermoelectric ceramics is mainly high temperature solid-phase sintering.Because oxide compound positively charged ion rate of diffusion is little, solid state reaction process is slow, and the method needs high temperature (T>1450 DEG C) long-time sintering repeatedly, causes grain-size larger, and density is lower, poor-performing.High-compactness can improve the electroconductibility of material, and grain-size I effectively suppresses the thermal conductivity of material, and therefore, seeking to prepare the method that density is high, grain-size is little is to improve at present the key of strontium titanate thermoelectric ceramics performance.
Discharge plasma sintering (Spark Plasma Sintering, be called for short SPS)---utilize pulsed current between particle, to excite high-temperature plasma to realize the process of sintering densification, be a kind of fast, the material new preparation technology of energy-saving and environmental protection, there is homogeneous heating, temperature rate is fast, and sintering time is short, production efficiency advantages of higher, be applicable to prepare very much high densification, the thermoelectric ceramic material of nanometer crystal grain.In addition, prepare uneven components in stupalith process for solving high temperature solid-phase sintering, the problem of time and effort consuming and energy dissipation, the method that can adopt sol-gel to add the moulding of spark discharge plasma sintering is prepared Strontium carbonate powder oxide thermoelectricity pottery.Than solid state reaction, sol-gel method can realization response thing in the even mixing of molecular level, system component be diffused in nanometer range, temperature of reaction is low, the grain diameter of preparation is little, distribution homogeneous.
Summary of the invention
The object of this invention is to provide a kind of density high (relative density >98%), little (average grain size <1 μ m), the preparation method of the N-type gadolinium strontium titanate doping oxide thermoelectricity pottery of thermoelectricity capability excellence of grain-size.
The present invention adopts following technical scheme for achieving the above object:
A preparation method for N-type gadolinium strontium titanate doping oxide thermoelectricity pottery, comprises the following steps:
(1) batching: according to general formula (Sr
1-xgd
x) TiO
3stoichiometric ratio calculate weigh contain required element raw material six water Gadolinium trinitrates, strontium nitrate and butyl (tetra) titanate, wherein x=0.05-0.1;
(2) preparation of precursor powder: six water Gadolinium trinitrates, strontium nitrate, Citric acid monohydrate Food grade are dissolved in appropriate amount of deionized water, and citric acid is 1-3:1 with whole metallic cations (containing Ti) molar ratio, and temperature obtains solution a after stirring; The mol ratio of controlling butyl (tetra) titanate and dehydrated alcohol is 1:5-20, and dehydrated alcohol and ethylene glycol mol ratio are 1:0.1-1, and the mixed solution of butyl (tetra) titanate and dehydrated alcohol and ethylene glycol is fully stirred and obtains solution b at normal temperatures; Solution b is slowly added drop-wise in above-mentioned solution a, stirs 3-8h at 60-80 DEG C and obtain faint yellow clarification mixing solutions, be placed on 180 DEG C of continuation in loft drier through 80-120 DEG C of still aging for some time and be dried, can obtain the xerogel that dark-brown is fluffy; By xerogel through grind after in retort furnace 900-1000 DEG C insulation 2-6h, obtain uniform precursor powder;
(3) preparation of ceramic female powder: the precursor powder that step (2) is obtained is placed in graphite boat, in argon gas or argon gas/hydrogen mixed gas atmosphere, 1000-1300 DEG C of reduction 1-5h obtain ceramic female powder;
(4) SPS sinter molding: the female powder of pottery that step (3) is obtained is put into the SPS graphite jig of diameter 20mm; after rising to 1200-1400 DEG C with the temperature rate of 50-100 DEG C/min, be incubated 1-30 minute; pressure selection 13-15MPa; argon gas atmosphere is protected, and obtains the cylindrical N-type gadolinium of the even compact strontium titanate doping oxide thermoelectricity pottery of diameter 20mm, thickness 0.5-10mm.
Beneficial effect of the present invention:
It is that thermoelectric ceramics method is compared that the present invention prepares Sr-Ti-O with traditional solid phase, and the method has reduced Gd doping SrTiO effectively
3the synthesis temperature of single-phase oxide, without repeatedly grinding or sintering, reduces energy consumption; Use SPS sinter molding, temperature rate is fast and have pressure sintering, reduces densification temperature and grain-size, when improved performance, enhances productivity.
Brief description of the drawings
Fig. 1 is target product (Sr
0.9gd
0.1) TiO
3pottery is after polishing thermal etching, and the photo of surperficial use emission scan electron microscope observation, shows that ceramic surface is without hole or crackle, and average grain size is less than 1 micron.
Fig. 2 is target product (Sr
0.9gd
0.1) TiO
3the XRD diffracting spectrum of ceramic bulk material, from XRD spectra, products therefrom is Perovskite Phase Strontium carbonate powder (JCPDS card No:01-084-0443).
Fig. 3 is target product (Sr
0.9gd
0.1) TiO
3ceramic thermoelectric figure of merit variation with temperature, as can be seen from the figure it is in 1000K left and right, and ZT value can reach 0.37.
Embodiment
Embodiment 1
The method of preparing Gd strontium titanate doping thermoelectric ceramics with combination of sol-gel discharge plasma sintering, completes following steps:
(1) batching: press general formula (Sr
0.9gd
0.1) TiO
3stoichiometric ratio calculate weigh contain required element raw material six water Gadolinium trinitrates, strontium nitrate and butyl (tetra) titanate;
(2) preparation of precursor powder: six water Gadolinium trinitrates, strontium nitrate, Citric acid monohydrate Food grade are dissolved in appropriate amount of deionized water, and citric acid and whole metallic cations (containing Ti) molar ratio 2.5:1, obtain solution a after stirring at normal temperature; The mol ratio 1:20 that controls butyl (tetra) titanate and dehydrated alcohol, dehydrated alcohol and ethylene glycol mol ratio are 1:0.1, will under the mixed solution normal temperature of butyl (tetra) titanate and dehydrated alcohol and ethylene glycol, fully be uniformly mixed and obtain solution b; Solution b is slowly added drop-wise in above-mentioned solution a, stirs 4h at 75 DEG C and obtain faint yellow clarification mixing solutions, be placed on 180 DEG C of continuation in loft drier through 80-120 DEG C of still aging for some time and be dried, can obtain the xerogel that dark-brown is fluffy; By xerogel through grind after in retort furnace 950 DEG C insulation 3h, obtain uniform precursor powder;
(3) preparation of ceramic female powder: the precursor powder that step (2) is obtained is placed in graphite boat, and 1200 DEG C of reductase 12 h obtain (hydrogen accounts for total volume fraction 5%) in argon gas/hydrogen mixed gas atmosphere;
(4) SPS sinter molding: the female powder of pottery that step (3) is obtained is put into the SPS graphite jig of diameter 20mm; after rising to 1375 DEG C with the temperature rate of 100 DEG C/min, be incubated 5 minutes; pressure selection 13MPa; argon gas atmosphere is protected, and obtains the cylindrical N-type gadolinium of the even compact strontium titanate doping oxide thermoelectricity pottery of diameter 20mm, thickness 0.5-10mm.
Claims (1)
1. a preparation method for N-type gadolinium strontium titanate doping oxide thermoelectricity pottery, is characterized in that comprising the following steps:
(1) batching: according to general formula (Sr
1-xgd
x) TiO
3stoichiometric ratio calculate weigh contain required element raw material six water Gadolinium trinitrates, strontium nitrate and butyl (tetra) titanate, wherein x=0.05-0.1;
(2) preparation of precursor powder: six water Gadolinium trinitrates, strontium nitrate, Citric acid monohydrate Food grade are dissolved in appropriate amount of deionized water, and citric acid and Sr+Gd+Ti molar ratio are 1-3:1, obtain solution a after stirring at normal temperature; The mol ratio of controlling butyl (tetra) titanate and dehydrated alcohol is 1:5-20, and dehydrated alcohol and ethylene glycol mol ratio are 1:0.1-1, and the mixed solution of butyl (tetra) titanate and dehydrated alcohol and ethylene glycol is fully stirred and obtains solution b at normal temperatures; Solution b is slowly added drop-wise in above-mentioned solution a, stirs 3-8h at 60-80 DEG C and obtain faint yellow clarification mixing solutions, be placed on 180 DEG C of continuation in loft drier through 80-120 DEG C of still aging for some time and be dried, can obtain the xerogel that dark-brown is fluffy; By xerogel through grind after in retort furnace 900-1000 DEG C insulation 2-6h, obtain uniform precursor powder;
(3) preparation of ceramic female powder: the precursor powder that step (2) is obtained is placed in graphite boat, in argon gas or argon gas/hydrogen mixed gas atmosphere, 1000-1300 DEG C of reduction 1-5h obtain ceramic female powder;
(4) SPS sinter molding: the female powder of pottery that step (3) is obtained is put into the SPS graphite jig of diameter 20mm; after rising to 1200-1400 DEG C with the temperature rate of 50-100 DEG C/min, be incubated 1-30 minute; pressure selection 13-15MPa; argon gas atmosphere is protected, and obtains the cylindrical N-type gadolinium of the even compact strontium titanate doping oxide thermoelectricity pottery of diameter 20mm, thickness 0.5-10mm.
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| CN104926298B (en) * | 2015-05-27 | 2017-08-29 | 中国石油化工股份有限公司青岛安全工程研究院 | One kind (Sr1‑xLnx)2TiO4Serial dense conductive oxide ceramics and preparation method thereof |
| CN112624756A (en) * | 2020-12-25 | 2021-04-09 | 中国工程物理研究院核物理与化学研究所 | Preparation method of ceramic strontium titanate isotope fuel pellet |
| CN113582582B (en) * | 2021-07-30 | 2022-03-08 | 湖南省新化县林海陶瓷有限公司 | Preparation process of electronic ceramic composite substrate with wide working temperature zone |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101423243A (en) * | 2008-11-25 | 2009-05-06 | 北京科技大学 | La doped SrTiO3 base oxide pyroelectric material and preparation method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101423243A (en) * | 2008-11-25 | 2009-05-06 | 北京科技大学 | La doped SrTiO3 base oxide pyroelectric material and preparation method |
Non-Patent Citations (2)
| Title |
|---|
| Noriyuki OKINAKA et al..Thermoelectric Properties of Rare Earth-doped SrTiO3 Using Combination of Combustion Synthesis (CS) and Spark Plasma Sintering (SPS).《ISIJ International》.2010,第50卷(第9期),第1300-1304页. * |
| Thermoelectric Properties of Rare Earth-doped SrTiO3 Using Combination of Combustion Synthesis (CS) and Spark Plasma Sintering (SPS);Noriyuki OKINAKA et al.;《ISIJ International》;20101231;第50卷(第9期);第1300-1304页 * |
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