CN1270978C - Preparation method of Ca3Co2O6 based oxide thermoelectric material - Google Patents

Preparation method of Ca3Co2O6 based oxide thermoelectric material Download PDF

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CN1270978C
CN1270978C CN 200410086892 CN200410086892A CN1270978C CN 1270978 C CN1270978 C CN 1270978C CN 200410086892 CN200410086892 CN 200410086892 CN 200410086892 A CN200410086892 A CN 200410086892A CN 1270978 C CN1270978 C CN 1270978C
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ca3co2o6
compound
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complexing agent
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CN1621354A (en
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张久兴
路清梅
刘科高
张隆
刘燕琴
周美玲
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Beijing University of Technology
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Beijing University of Technology
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Abstract

The present invention relates to a method for preparing Ca3Co2O6 group oxide thermoelectric materials, which belongs to the field of oxide thermoelectric materials. A solid phase synthesis method has the disadvantages of higher reaction temperature, long reaction time, poor chemical homogeneity and high energy consumption, and can not easily obtain fine grain sizes. After Ca<2+>, Co<2->, citric acid or tartaric acid as a complexing agent, and hexanediol or Tween as a surface dispersing agent are dissolved, the pH is regulated between 1.2 and 3.5, wherein the ratio of Ca<2+> to Co<2-> is 3:2, the molar ratio of the complexing agent to Ca<2+>+Co<2-> is 1 to 2:1, and the weight of the surface dispersing agent accounts for 1 to 5% of that of final products; gel is formed by concentration; after grinding, organic substances and nitrate are removed through pretreatment at a temperature of 400 to 600 DEG C; the temperature rises to be a temperature of 900 to 950 DEG C, and Ca3Co2O6 oxide powder is obtained through calcination; the Ca3Co2O6 oxide powder is filled in a mould, pressed and is sintered by electric discharge plasma; and the sintering conditions are in that the temperature rise rate is from 130 to 150 DEG C /min, the temperature is from 850 to 900 DEG C, and the temperature holding time is from 3 to 10 min. Under the conditions with lower reaction temperature and shorter reaction time, the present invention can synthesize the Ca3Co2O6 group oxide thermoelectric material with high chemical homogeneity and uniform crystal grain.

Description

A kind of Ca 3Co 2O 6The preparation method of base oxide pyroelectric material
Technical field
The present invention relates to a kind of Ca 3Co 2O 6The preparation method of base oxide pyroelectric material comprises Ca 3Co 2O 6And doping Ca 3Co 2O 6The synthetic method of base oxide pyroelectric material belongs to the oxide pyroelectric material preparing technical field.
Background technology
The chapter that people use thermoelectric material has been opened in the discovery of thermoelectric effect in 1823.After 1950's, thermoelectric material has obtained using widely in each technical field, as the thermoelectric power generation of vehicle exhaust and other industrial exhaust heats, and in electronic technology, industry and vacuum technique, agriculture and biological, medical treatment, commerce, the thermoelectric refrigeration in the fields such as national defence.The thermoelectricity capability of material is represented by thermoelectric figure of merit Z usually:
Z＝α 2σ/κ
Wherein α is the Seebeck coefficient, and κ is a thermal conductivity, and σ is a specific conductivity.Because the Z value of material is different under the varying environment temperature, the size of people's Seebeck coefficient commonly used and temperature is amasss-zero dimension thermoelectric figure of merit ZT is described the quality of pyroelectric material performance traditionally.More satisfactory thermoelectric material must have higher Seebeck coefficient and specific conductivity, simultaneously low thermal conductivity should be arranged.
In the thermoelectric material of research, the thermoelectricity capability of intermetallic compound is superior in the thermoelectric material at present.But because their temperature of fusion, decomposition temperature is very low, resistance to oxidation not, what have also contains poisonous or rare elements, and transformation efficiency is very low in the temperature range of 600K-1000K, so they are very limited in the application of used heat conversion aspect.In recent years, many promising novel thermoelectric compounds develop in succession, comprise the compound of uhligite, clathrate compound and some laminate structures etc., wherein oxide compound is because its high high-temp stability, oxidation-resistance and nontoxicity, can long term operation under high temperature in the oxidizing atmosphere, and preparation is simple, can be directly in air advantage such as sintering and be subjected to people's favor.There has been multiple oxide system to obtain research, as NaCo 2O 4Deng, Ca wherein 3Co 2O 6Compound is again because its particular structure and high temperature (1300K) chemical stability, and higher thermoelectricity capability and be subjected to scholar's growing interest.
Ca 3Co 2O 6Compound has the physical property of part one-dimensional material, promptly has each very strong diversity and unique physical property; In addition, under the situation that the Seebeck coefficient reduces with the rising of temperature, its Seebeck coefficient under 1073K is still up to 160 μ V/K; Moreover, Ca 3Co 2O 6Structure is also perpendicular to one dimension Co 2O 6 6-Introduce the phon scattering of certain form on the direction of chain, improved the thermal conductivity of this compounds.Therefore be a kind of extremely promising thermoelectric material.Current, Ca 3Co 2O 6Solid reaction process is adopted in the preparation of compound thermoelectric material mostly, adopts solid-phase synthesis to prepare Ca as people such as M.Mikami 3Co 2O 6Monocrystalline (M.Mikami, R.Funahashi, M.Yoshimura, et.al, Journal of Applied Physics, Vol.94, No.10 (2003) pp.6579-6582), and studied Ca 3Co 2O 6Monocrystalline thermoelectricity capability at high temperature.Experimental result shows, when temperature when 300K rises to 1073K, resistivity 2*10 4Ω is from reducing to 8m Ω.Seebeck coefficient is for just, and at 373K, 1073K is respectively 230 μ V/K, 160 μ V/K.Thermal conductivity κ is at room temperature low to be 8W/mK, descends with the rising of temperature is linear, reduces to 4.6W/mK during 773K.Its highest ZT value under 1073K can reach 0.15.People such as Kouta Iwasaki have studied doping Cr by solid-phase synthesis, Cu, and La, elements such as Bi are to Ca 3Co 2O 6The influence of preparation, lattice parameter and thermoelectricity capability.Cr is mixed in discovery, La, and lattice parameter increases to some extent behind the Bi, and the lattice parameter of doped with Cu is constant substantially, Ca 3Co 2O 6Resistivity 1.6 * 10 2Ω m～1.3 * 10 -3Change in the scope of Ω m, after the doped with Cu, Ca 3Co 2O 6Power factor (power factor) be increased to 3.4 * 10 -5W/mK 2These work all are that the further investigation of such thermoelectric material is from now on laid a good foundation.
But, when adopting solid reaction process, for obtaining the homogeneous single phase product, generally need repeat to grind and long-time roasting, thereby cause process cycle to grow (Physical Review B, Vol.61, No.19 (2000) pp.R12551-12554) usually, problems such as product is impure, and grain fineness number is restive.And mechanical milling process introduces impurity easily, is difficult to accurately control product quality.
In a word, traditional solid phase synthesis process exists that temperature of reaction is higher, the reaction times is relatively long and chemical uniformity is bad, energy consumption is big, is difficult to obtain a series of problems of fine grain size thermoelectric compound.
Summary of the invention
The objective of the invention is the problems that exist in the existing solid phase method synthesis oxide thermoelectric material technology, provide a kind of sol-gel method that utilizes to synthesize Ca 3Co 2O 6Base oxide pyroelectric material comprises Ca 3Co 2O 6And doping Ca 3Co 2O 6The method of base oxide pyroelectric material, in lower temperature of reaction and under than the short reaction times, the Ca of synthetic a kind of chemical uniformity height, uniform crystal particles 3Co 2O 6Base oxide pyroelectric material is then by discharge plasma sintering (SPS) method, fast with powder sintered one-tenth block materials.
A kind of Ca 3Co 2O 6The preparation method of base oxide pyroelectric material is characterized in that, is made up of following steps:
(1) be 3: 2 ratio with raw material in calcium ion and cobalt ion mol ratio, with complexing agent citric acid or tartrate, wherein complexing agent: total metal ion (Ca 2++ Co 2+) mol ratio be 1～2: 1, and account for final product Ca 3Co 2O 6The surface dispersant ethylene glycol of base oxide pyroelectric material weight 1～5% or tween-80 dissolve together and are mixed with mixing solutions, after treating to dissolve fully, drip pH value conditioning agent down in stirring, and transfer to pH=1.2～3.5, and reaction obtains forerunner's colloidal sol;
(2) the forerunner's colloidal sol that obtains is concentrated the formation gel through conventional technology;
(3) with the gel that makes after grinding, earlier 400～600 ℃ down through conventional pre-treatment to remove organism and nitrate wherein, be warmed up to 900～950 ℃ of calcinings again and promptly obtain Ca 3Co 2O 6Oxide powder;
(4) powder after the above-mentioned calcining is packed in the mould, compacting is sintered directly into bulk material with discharging plasma sintering equipment, and sintering condition is 130～150 ℃/min of temperature rise rate, 850～900 ℃ of temperature, soaking time 3～10min.
The content of complexing agent and pH value of solution value conditioning agent is very crucial in the step (1).When the complexing agent add-on is C/M=1, pH=1.2～3.5; During C/M=2, suitable pH scope is 1.4～2.7.
Adopt above processing method, prepared Ca with following physicochemical characteristic 3Co 2O 6The oxide compound block thermoelectric material:
(1) molecular formula: Ca 3Co 2O 6
(2) particle diameter of calcining back powder oxide is 100～300nm;
(3) behind discharge plasma sintering, the grain size of block is 1～4 μ m, at 700 ℃ of following Ca 3Co 2O 6Zero dimension thermoelectric figure of merit ZT reach 0.02.
Adulterated Ca 3Co 2O 6The preparation method of base oxide pyroelectric material is characterized in that, is made up of following steps:
(1) various nitrate raw material is pressed molecular formula M xCa 3-xCo 2O 6, M=Cu wherein, Ag, La, Ce, the cationic proportion of x=0.05～0.5, with complexing agent citric acid or tartrate, wherein complexing agent: the mol ratio of total metal ion is 1～2: 1, and and accounts for final product Ca 3Co 2O 6The surface dispersant ethylene glycol of base oxide pyroelectric material weight 1～5% or tween-80 dissolve together and are mixed with mixing solutions, after treating to dissolve fully, drip pH value conditioning agent down in stirring, and make the pH value of solution value reach 1.2～3.5, continue reaction and promptly obtain forerunner's colloidal sol;
(2) the forerunner's colloidal sol that obtains is concentrated, form gel;
(3) with the gel that makes after grinding, earlier 400～600 ℃ down through conventional pre-treatment to remove organism and nitrate wherein, be warmed up to 900～950 ℃ of calcinings again and promptly obtain adulterated Ca 3Co 2O 6The base oxide powder;
(4) powder after the above-mentioned calcining is packed in the mould, compacting sinters bulk into discharging plasma sintering equipment
Material, sintering condition are 130～150 ℃/min of temperature rise rate, 800～900 ℃ of temperature, soaking time 3～10min.
Adopt above step, prepared a series of adulterated cobalt base oxide thermoelectric materials, have following physical chemical characteristics:
(1) molecular formula: M xCa 3-xCo 2O 6, M=Cu wherein, Ag, La, Ce, x=0.05～0.5;
(2) particle diameter of calcining back powder oxide is 100～300nm;
(3) behind discharge plasma sintering, the grain-size of block is 1～5 μ m, reaches 0.01～0.02 at 700 ℃ of following zero dimension thermoelectric figure of merit ZT.
Ca 3Co 2O 6The preparation method of base oxide pyroelectric material and adulterated Ca 3Co 2O 6Preparation method's difference of base oxide pyroelectric material only is the difference of raw material.
Compared with prior art, the present invention has following advantage: adopt the synthetic Ca of colloidal sol-gel-SPS method 3Co 2O 6Base oxide and doping Ca 3Co 2O 6Base oxide pyroelectric material, in the preparation of forerunner's powder, has short, characteristic of low energy consumption of simple to operate, reaction times, high, the good uniformity of forerunner's powder chemistry stability of preparation, particle diameter less (100～300nm), when particularly adopting discharge plasma to sinter block materials into, more demonstrate advantages such as sintering velocity is fast, time weak point, products therefrom single phase property height, the grain size of block materials is 0.5～5 μ m behind the sintering, reaches 0.01～0.02 at 700 ℃ of following zero dimension thermoelectric figure of merit ZT.
Description of drawings
Fig. 1. embodiment 1 gained Ca 3Co 2O 6The XRD figure spectrum of compound.
Fig. 2. embodiment 1 gained Ca 3Co 2O 6The fracture SEM pattern of compound.
Fig. 3. embodiment 2 gained Ca 3Co 2O 6The XRD figure spectrum of compound.
Fig. 4. embodiment 2 gained Ca 3Co 2O 6The fracture SEM pattern of compound.
Fig. 5. embodiment 3 gained Ca 3Co 2O 6The XRD figure spectrum of compound.
Fig. 6. embodiment 3 gained Ca 3Co 2O 6The fracture SEM pattern of compound.
Fig. 7. embodiment 4 gained Ca 3Co 2O 6The XRD figure spectrum of compound.
Fig. 8. embodiment 4 gained Ca 3Co 2O 6The fracture SEM pattern of compound.
Fig. 9. embodiment 5 gained La 0.1Ca 2.9Co 4O 9The XRD figure spectrum of compound.
Figure 10. embodiment 5 gained La 0.1Ca 2.9Co 4O 9The fracture SEM pattern of compound.
Figure 11. embodiment 6 gained Cu 0.05Ca 2.9Co 4O 9The XRD figure spectrum of compound.
Figure 12. embodiment 6 gained Cu 0.05Ca 2.9Co 4O 9The SEM collection of illustrative plates of compound fracture.
Figure 13. embodiment 7 gained Ce 0.2Ca 2.8Co 4O 9The XRD figure spectrum of compound.
Figure 14. embodiment 8 gained Ag 0.5Ca 2.7Co 4O 9The XRD figure spectrum of compound.
Embodiment
Below the raw material that adopts among all embodiment be commercially available analytical pure raw material.
[embodiment 1] Ca 3Co 2O 6The preparation of compound
Accurately take by weighing 1.18 gram Ca (NO 3) 24H 2O, 0.97 gram Co (NO 3) 26H 2O, 0.5 milliliter of CH 3CH 2OH and 1.75 gram C 6H 8O 7H 2O, place reaction vessel, to wherein adding 49.5 ml deionized water, after treating that above-mentioned raw materials fully dissolves, slowly drip the ammoniacal liquor (water: the strong aqua volume ratio is 1: 2) for preparing down in continuous stirring, when the pH value of solution value reaches 1.2, stop dropping ammonia, continue to stir 1 hour, obtain the limpid colloid of light violet magenta.The further stirring of the colloid that obtains concentrated, promptly get xerogel.Xerogel is pulverized, put into 400 ℃ of following pre-treatment of retort furnace 2 hours, be heated to 950 ℃ and be incubated 2 hours then, promptly obtain required Ca 3Co 2O 6Powder.At last this powdered product is ground, in the mould of packing into, put into discharge plasma sintering (SPS) stove, be heated to 900 ℃ and be incubated 3min and promptly obtain Ca with the temperature rise rate of 130 ℃/min 3Co 2O 6Block thermoelectric material.Ca 3Co 2O 6The thing of compound block reaches fracture apperance mutually and sees Fig. 1 and Fig. 2, and thing shows as Ca mutually substantially 3Co 2O 6Phase structure, grain size are 2～3 microns.Under 700 ℃, the ZT value of this compound reaches 0.022.
[embodiment 2] Ca 3Co 2O 6The preparation of compound
Accurately take by weighing 1.18 gram Ca (NO 3) 24H 2O, 0.97 gram Co (NO 3) 26H 2O, 0.5 milliliter of CH 3CH 2OH and 3.5 gram C 6H 8O 7H 2O, place beaker, to wherein adding 49.0 ml deionized water, after treating that above-mentioned raw materials fully dissolves, slowly drip the ammoniacal liquor (water: the strong aqua volume ratio is 1: 2) for preparing down in continuous stirring, when the pH value of solution value reaches 2.7, stop dropping ammonia, continue stirring and obtain the scarlet transparent colloid.The colloid that obtains is continued the concentrated xerogel that promptly gets.Xerogel is pulverized, put into 500 ℃ of following pre-treatment of retort furnace 2 hours, be heated to 900 ℃ and be incubated 4 hours then, promptly obtain required Ca 3Co 2O 6Powder.At last this powdered product is ground, in the mould of packing into, put into discharge plasma sintering (SPS) stove, be heated to 900 ℃ and be incubated 5min and promptly obtain Ca with the temperature rise rate of 140 ℃/min 3Co 2O 6Block thermoelectric material.Ca 3Co 2O 6The thing of compound block reaches fracture apperance mutually and sees Fig. 3 and 4, shows as Ca substantially 3Co 2O 6Phase structure, grain size are about 1 micron.Under 700 ℃, the ZT value of this compound reaches 0.014.
[embodiment 3] Ca 3Co 2O 6The preparation of compound
Accurately take by weighing 1.18 gram Ca (NO 3) 24H 2O, 0.97 gram Co (NO 3) 26H 2O, 1.0 milliliters of C 64H 124O 26Reach 0.875 gram C 6H 8O 7H 2O, place beaker, to wherein adding 49.0 ml deionized water, after treating that above-mentioned raw materials fully dissolves, slowly drip the ammoniacal liquor (water: the strong aqua volume ratio is 1: 2) for preparing down in continuous stirring, when the pH value of solution value reaches 3.5, stop dropping ammonia, continue stirring and obtain the limpid colloid of light red.The colloid that obtains is continued the concentrated xerogel that promptly gets.Xerogel is pulverized, put into 600 ℃ of following pre-treatment of retort furnace 2 hours, be heated to 900 ℃ and be incubated 8 hours then, promptly obtain required Ca 3Co 2O 6Powder.At last this powdered product is ground, in the mould of packing into, put into discharge plasma sintering (SPS) stove, be heated to 950 ℃ and be incubated 5min and promptly obtain Ca with the temperature rise rate of 150 ℃/min 3Co 2O 6Block thermoelectric material.Ca 3Co 2O 6The thing of compound block reaches fracture apperance mutually and sees Fig. 5 and 6.Product shows as Ca 3Co 2O 6Phase structure, grain size are about 0.5～1.5 micron.Under 700 ℃, the ZT value of this compound reaches 0.018.
[embodiment 4] Ca 3Co 2O 6The preparation of compound
Accurately take by weighing 1.18 gram Ca (NO 3) 24H 2O, 0.97 gram Co (NO 3) 26H 2O, 1.0 milliliters of C 64H 124O 26Reach 0.835 gram C 4H 6O 8, place beaker, to wherein adding 49.5 ml deionized water, after treating that above-mentioned raw materials fully dissolves, slowly drip the ammoniacal liquor (water: the strong aqua volume ratio is 1: 2) for preparing down in continuous stirring, when the pH value of solution value reaches 1.4, stop dropping ammonia, continue stirring and obtain red limpid colloid.The colloid that obtains is continued the concentrated xerogel that promptly gets.Xerogel is pulverized, put into 500 ℃ of following pre-treatment of retort furnace 2 hours, be heated to 950 ℃ and be incubated 2 hours then, promptly obtain required Ca 3Co 2O 6Powder.At last this powdered product is ground, in the mould of packing into, put into discharge plasma sintering (SPS) stove, be heated to 900 ℃ and be incubated 10min and promptly obtain Ca with the temperature rise rate of 150 ℃/min 3Co 2O 6Block thermoelectric material.Ca 3Co 2O 6The thing of compound block reaches fracture apperance mutually and sees Fig. 7 and Fig. 8.Product shows as Ca 3Co 2O 6Phase structure, grain size are about 1.5～3 microns.Under 700 ℃, the ZT value of this compound reaches 0.016.
[embodiment 5] La 0.1Ca 2.9Co 2O 6The preparation of compound
Accurately take by weighing 9.12 gram Ca (NO 3) 24H 2O, 7.76 gram Co (NO 3) 26H 2O, 0.577 gram La (NO 3) 36H 2O, 14.00 gram C 6H 8O 7H 2O and 5.0 milliliters of C 64H 124O 26, place reaction vessel, to wherein adding 195.0 ml deionized water, after treating fully dissolving, slowly drip the ammoniacal liquor (water: the strong aqua volume ratio is 1: 2) for preparing down in continuous stirring, when the pH value of solution value reaches 2.0, stop dropping ammonia, continue stirring and obtain the red-purple colloid.The colloid that obtains is continued the concentrated xerogel that promptly gets.After at last xerogel being pulverized, put into 500 ℃ of following pre-treatment of retort furnace 2 hours, be heated to 950 ℃ and be incubated 2 hours then, the powdered product after the calcining is ground, pack in the mould, put into the SPS sintering oven and be heated to 900 ℃ and be incubated 5min and promptly obtain La with the temperature rise rate of 150 ℃/min 0.1Ca 2.9Co 2O 6Block thermoelectric material.La 0.1Ca 2.9Co 2O 6The thing of compound block reaches fracture apperance mutually and sees Fig. 9 and Figure 10 respectively.Product shows as Ca 3Co 2O 6Phase structure, grain size are about 1～2 micron.Under 700 ℃, the ZT value of this compound reaches 0.015.
[embodiment 6] Cu 0.05Ca 2.95Co 2O 6The preparation of compound
Accurately take by weighing 9.28 gram Ca (NO 3) 24H 2O, 7.76 gram Co (NO 3) 26H 2O, 0.24 gram Cu (NO 3) 26H 2O, 13.50 gram C 6H 8O 7H 2O and 5.0 milliliters of C 64H 124O 26Place reaction vessel, to wherein adding 195.0 ml deionized water, after treating that above-mentioned raw materials fully dissolves, in the slow down pH value that drips ammoniacal liquor (water: the strong aqua volume ratio is 1: the 2) regulator solution for preparing of continuous stirring, when solution ph reaches 2.0, stop dropping ammonia, continue stirring and obtain forerunner's colloid, the colloid that obtains is further concentrated promptly get xerogel.After at last xerogel being pulverized, put into 500 ℃ of following pre-treatment of retort furnace 2 hours, be warming up to 950 ℃ and be incubated 2 hours then, powdered product after will calcining at last grinds, pack in the graphite jig, put into the SPS sintering oven, be heated to 900 ℃ and be incubated 5min and promptly obtain Cu with the temperature rise rate of 150 ℃/min 0.1Ca 2.9Co 2O 6Block thermoelectric material.Cu 0.1Ca 2.9Co 2O 6The thing of compound block reaches fracture apperance mutually and sees Figure 11 and Figure 12 respectively, and product shows as Ca 3Co 2O 6Phase structure, grain size are about 2～3 microns.Under 700 ℃, the ZT value of this compound reaches 0.013.
[embodiment 7] Ce 0.2Ca 2.8Co 2O 6The preparation of compound
Accurately take by weighing 8.80 gram Ca (NO 3) 24H 2O, 7.76 gram Co (NO 3) 26H 2O, 1.15 gram Ce (NO3) 36H 2O, 13.00 gram C 6H 8O 7H 2O and 5.0 milliliters of C 64H 124O 26Place reaction vessel, to wherein adding 195.0 ml deionized water, after treating that above-mentioned raw materials fully dissolves, in the slow down pH value that drips ammoniacal liquor (water: the strong aqua volume ratio is 1: the 2) regulator solution for preparing of continuous stirring, when solution ph reaches 1.8, stop dropping ammonia, continue stirring and obtain forerunner's colloid, the colloid that obtains is further concentrated promptly get xerogel.After at last xerogel being pulverized, put into 500 ℃ of following pre-treatment of retort furnace 2 hours, be warming up to 900 ℃ and be incubated 2 hours then, powdered product after will calcining at last grinds, pack in the graphite jig, put into the SPS sintering oven, be heated to 900 ℃ and be incubated 5min and promptly obtain Ce with the temperature rise rate of 150 ℃/min 0.2Ca 2.8Co 2O 6Block thermoelectric material.Ce 0.2Ca 2.8Co 2O 6The phase structure of compound block is seen Figure 13, shows as single-phase Ca substantially 3Co 2O 6Structure, under 700 ℃, the ZT value of this compound reaches 0.013.
[embodiment 8] Ag 0.5Ca 2.5Co 2O 6The preparation of compound
Accurately take by weighing 14.15 gram Ca (NO 3) 24H 2O, 7.76 gram Co (NO 3) 26H 2O, 1.13 gram AgNO 3, 14.50 gram C 6H 8O 7H 2O and 5.0 milliliters of C 64H 124O 26, place reaction vessel, to wherein adding 195.0 ml deionized water, treat that fully the dissolving back slowly drips the ammoniacal liquor (water: the strong aqua volume ratio is 1: 2) for preparing down in continuous stirring, when the pH value of solution value reaches 2.1, stop dropping ammonia, continue stirring and obtain forerunner's vitreosol.With the further concentrate drying of the colloid that obtains, obtain forerunner's gel.At last xerogel is pulverized, put into 600 ℃ of following pre-treatment of retort furnace 2 hours, be warming up to 900 ℃ and be incubated 2 hours then, powdered product after will calcining at last grinds, pack in the graphite jig, put into the SPS sintering oven, be heated to 850 ℃ and be incubated 10min and promptly obtain Ag with the temperature rise rate of 150 ℃/min 0.3Ca 2.7Co 2O 6Block thermoelectric material.Ag 0.3Ca 2.7Co 2O 6The phase structure of compound block is seen Figure 14, shows as single-phase Ca substantially 3Co 2O 6Structure, under 700 ℃, the ZT value of this compound reaches 0.014.

Claims (2)

1, a kind of Ca 3Co 2O 6The preparation method of base oxide pyroelectric material is characterized in that, is made up of following steps:
1) be 3: 2 ratio with raw material in calcium ion and cobalt ion mol ratio, with complexing agent citric acid or tartrate, wherein complexing agent: total metal ion is Ca 2+And Co 2+Total mol ratio be 1～2: 1, and account for final product Ca 3Co 2O 6The surface dispersant ethylene glycol of base oxide pyroelectric material weight 1～5% or tween-80 dissolve together and are mixed with mixing solutions, after treating to dissolve fully, drip pH value conditioning agent down in stirring, and transfer to pH=1.2～3.5, and reaction obtains forerunner's colloidal sol;
2) the forerunner's colloidal sol that obtains is concentrated the formation gel;
3) with the gel that makes after grinding, earlier 400～600 ℃ down through pre-treatment to remove organism and nitrate wherein, be warmed up to 900～950 ℃ of calcinings again and promptly obtain Ca 3Co 2O 6Oxide powder;
4) powder after the above-mentioned calcining is packed in the mould, compacting is sintered directly into bulk material with discharging plasma sintering equipment, and sintering condition is 130～150 ℃/min of temperature rise rate, 850～900 ℃ of temperature, soaking time 3～10min.
2, a kind of Ca according to claim 1 3Co 2O 6The preparation method of base oxide pyroelectric material is characterized in that, complexing agent in the step 1): total metal ion is Ca 2+And Co 2+Total mol ratio be 2 o'clock, suitable pH scope is 1.4～2.7.
CN 200410086892 2004-11-05 2004-11-05 Preparation method of Ca3Co2O6 based oxide thermoelectric material Expired - Fee Related CN1270978C (en)

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CN101597088B (en) * 2009-07-06 2010-11-03 武汉理工大学 Preparation method of nanometer Bi2Sr2Co2Oy thermo-electricity compound powder
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CN106077694B (en) * 2016-08-08 2017-11-28 南昌大学 A kind of preparation method of spherical cobalt powder
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