CN111653662A - GeTe-based thermoelectric material with pseudo-cubic phase structure and preparation method thereof - Google Patents
GeTe-based thermoelectric material with pseudo-cubic phase structure and preparation method thereof Download PDFInfo
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- 239000000463 material Substances 0.000 title claims abstract description 104
- 229910005900 GeTe Inorganic materials 0.000 title claims abstract description 67
- 238000002360 preparation method Methods 0.000 title abstract description 14
- 239000000126 substance Substances 0.000 claims abstract description 23
- 239000002994 raw material Substances 0.000 claims description 49
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- 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
- H10N10/852—Thermoelectric active materials comprising inorganic compositions comprising tellurium, selenium or sulfur
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B19/00—Selenium; Tellurium; Compounds thereof
- C01B19/002—Compounds containing, besides selenium or tellurium, more than one other element, with -O- and -OH not being considered as anions
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- C01—INORGANIC CHEMISTRY
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- 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
Abstract
The invention discloses a GeTe-based thermoelectric material with a pseudo-cubic phase structure and a preparation method thereof, wherein the chemical formula of the thermoelectric material is Ge0.90‑xTixSb0.10Te, wherein the value range of x is more than or equal to 0 and less than or equal to 0.03. The invention also provides a preparation method of the GeTe-based thermoelectric material with the pseudo-cubic phase structure. The invention makes the crystal structure of the GeTe-based thermoelectric material changed by adding Ti element and controlling the content of Ti element, and effectively changes the room temperature crystal structure of the GeTe-based thermoelectric material into a pseudo cubic phase structure. The GeTe-based thermoelectric material with the pseudo-cubic phase structure is lead-free, has a stable pseudo-cubic phase structure at room temperature, has low thermal conductivity, has good thermoelectric performance within a working temperature range, and has excellent application prospect.
Description
Technical Field
The invention relates to a lead-free thermoelectric material and a preparation method thereof, in particular to a GeTe-based thermoelectric material and a preparation method thereof, which are applied to the technical field of new energy functional materials and preparation processes thereof.
Background
Since the industrial revolution, the world economy has been rapidly developed, fossil energy has been exhausted, and the problem of environmental pollution caused by the use of fossil energy has become more and more significant, so that new energy materials are urgently needed in the human society. The thermoelectric material is a functional material capable of converting electric energy and thermal energy to each other, and is based on the seebeck effect and the peltier effect. The thermoelectric device based on the material has the remarkable advantages of small volume, no pollution, no noise, no moving parts and the like, and has good application prospect.
The application of the prior thermoelectric material-based device is limited due to low conversion efficiency, and the optimization of the thermoelectric performance of the thermoelectric material is the key for improving the conversion efficiency. The performance of thermoelectric materials is generally measured by a dimensionless figure of merit, zT ═ S2σ T/κ, where T, S, σ, κ are the absolute temperature, Seebeck coefficient of the material, electrical conductivity, and thermal conductivity, respectively. A high-performance thermoelectric material is required to have a high seebeck coefficient, electric conductivity, and low thermal conductivity.
PbTe and PbSe are used as intermediate-temperature semiconductor thermoelectric materials with good thermoelectric performance, can be used for a temperature difference power generation device working in a temperature range (400-800K), and are already applied to the fields of industrial waste heat conversion and the like. However, since the PbTe-based thermoelectric material contains toxic Pb, GeTe has a better prospect than PbTe, and has higher electrical conductivity and higher thermal conductivity, so that the thermoelectric figure of merit is not high, and the phase transition problem also exists.
GeTe has intrinsic Ge vacancy, has higher carrier concentration, and has good electrical performance, but has high thermal conductivity, so the intrinsic GeTe thermoelectric material has low performance. Therefore, it is necessary to provide an optimized GeTe-based thermoelectric material and a method for preparing the same, which does not contain lead, has low thermal conductivity, and has a stable structure, thereby having high thermoelectric performance and stability, and thus the present invention is a technical problem to be solved.
Disclosure of Invention
In order to solve the problems of the prior art, the invention aims to overcome the defects in the prior art and provide a GeTe-based thermoelectric material with a pseudo-cubic phase structure and a preparation method thereof.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
a GeTe-based thermoelectric material with pseudo-cubic phase structure has a chemical formula of Ge0.90-xTixSb0.10Te, wherein the value range of x is more than or equal to 0 and less than or equal to 0.03. The invention converts the room temperature crystal structure of the GeTe-based thermoelectric material into a pseudo cubic phase structure.
The preferable value range of x is more than or equal to 0.01 and less than or equal to 0.03.
The optimal value of x is 0.02.
The invention also provides a preparation method of the pseudo cubic phase structure GeTe based thermoelectric material, which comprises the following steps:
a. preparing a metal raw material vacuum tube sealing:
according to the numerical value of x of the chemical formula of the prepared target thermoelectric material, respectively weighing the metal simple substances Ge, Sb, Ti and Te with the purity of not less than 99.99% according to the stoichiometric ratio, sequentially placing the raw materials of each component in a clean quartz tube, and performing vacuum sealing through a vacuum tube sealing machine for later use;
b. melting and quenching treatment of metal raw materials:
heating the well-sealed quartz tube filled with the raw material metal material prepared in the step a to melt and react the raw material, and then quenching in cold water to obtain a quenched ingot;
c. and (3) ingot casting diffusion annealing treatment:
sealing the ingot subjected to quenching treatment in the step b in a quartz tube in vacuum, annealing at high temperature, and then slowly cooling to room temperature to obtain an annealed ingot;
SPS sintering:
and c, grinding the ingot after annealing treatment in the step c into powder, placing the powder in a graphite mold, performing discharge plasma sintering, and cooling to room temperature to obtain the bulk GeTe-based thermoelectric material with the pseudo-cubic phase structure.
In the step b, the quartz tube filled with the raw materials is heated to 900-1000 ℃ at the speed of 100-150 ℃/h, and the temperature is kept for 1-2 days, so that the raw materials are fully reacted in a molten state.
In the step b, the quartz tube containing the raw materials is heated to 950 ℃ at the rate of 120 ℃/h, and the temperature is kept for 24h, so that the raw materials are fully reacted in a molten state.
In the step c, the quartz tube with the ingot is heated to 600-700 ℃ at the speed of 100-150 ℃/h, and is subjected to heat preservation for 2-4 days for high-temperature diffusion annealing.
In the step c, the quartz tube with the ingot is heated to 700 ℃ at the speed of 120 ℃/h, and is kept warm for 3 days, and high-temperature diffusion annealing is carried out.
In the step d, the temperature is increased to 500-550 ℃ at the speed of 100-200 ℃/min, the pressure is adjusted to 50-60 Mpa, the mixture is kept at constant temperature and constant pressure for at least 5min, and then spark plasma sintering is carried out.
As a further preferable technical scheme of the invention, in the step d, the temperature is increased to 500 ℃ at the speed of 100 ℃/min, the pressure is adjusted to 50Mpa, and the mixture is kept for 5min at constant temperature and constant pressure to carry out spark plasma sintering.
The thermoelectric material with the pseudo-cubic phase structure GeTe base optimizes the thermoelectric property of the thermoelectric material, the thermal conductivity of the material needs to be obviously reduced while the electrical property of the material is regulated, GeTe has intrinsic Ge vacancies, the carrier concentration is higher, and the thermal conductivity is very high although the material has good electrical property, so the property of the intrinsic GeTe thermoelectric material is not high. The invention provides a method for optimizing the electrical property of a GeTe-based thermoelectric material and simultaneously remarkably reducing the thermal conductivity of the GeTe-based thermoelectric material, and the room-temperature crystal structure of the GeTe-based thermoelectric material is converted into a pseudo cubic phase structure. High-valence atoms are doped at the Ge position, so that the carrier concentration is obviously reduced, the electrical property is optimized, and meanwhile, point defects, quality and strain fluctuation caused by introduction of various doped atoms result in low lattice thermal conductivity, and the performance of the GeTe-based thermoelectric material is improved. The lattice distortion caused by the doping atoms enables the GeTe-based thermoelectric material to be converted into a pseudo-cubic phase structure at room temperature. The work lays a foundation for further research of GeTe-based thermoelectric materials.
Compared with the prior art, the invention has the following obvious and prominent substantive characteristics and remarkable advantages:
1. the thermoelectric material is a P-type GeTe thermoelectric material with high carrier concentration, and the carrier concentration of the thermoelectric material is regulated and controlled to an optimal range by proper doping elements, so that the electrical property of the material is optimized;
2. according to the invention, by adding Ti and controlling the content of Ti, the crystal structure of the GeTe-based thermoelectric material is changed, and the room-temperature crystal structure of the GeTe-based thermoelectric material is effectively changed into a pseudo cubic phase structure; meanwhile, the lattice thermal conductivity of the material is further reduced by doping Ti element, and the thermoelectric figure of merit reaches 1.9 at 733K, so that the application of the GeTe-based thermoelectric material is laid;
3. the method is simple and easy to implement, low in cost and suitable for popularization and application.
Drawings
FIG. 1 shows Ge of the present invention0.90-xTixSb0.10X-ray diffraction pattern of Te thermoelectric material.
FIG. 2 shows Ge of the present invention0.90-xTixSb0.10The electrical conductivity of the Te thermoelectric material is plotted against temperature change.
FIG. 3 shows Ge of the present invention0.90-xTixSb0.10The Seebeck coefficient of the Te thermoelectric material is shown in a graph in relation to temperature change.
FIG. 4 shows Ge of the present invention0.90-xTixSb0.10A plot of seebeck coefficient versus carrier concentration for Te thermoelectric materials.
FIG. 5 shows Ge of the present invention0.90-xTixSb0.10The total thermal conductivity of the Te thermoelectric material is plotted against temperature change.
FIG. 6 shows Ge of the present invention0.90-xTixSb0.10The relationship between the lattice thermal conductivity of the Te thermoelectric material and the temperature change is shown schematically.
FIG. 7 shows Ge of the present invention0.90-xTixSb0.10A graph showing the relationship between the dimensionless figure of merit zT of the Te thermoelectric material and the temperature change.
Detailed Description
The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below:
the first embodiment is as follows:
in this embodiment, a high performance GeTe based thermoelectric material has a chemical formula of Ge0.90Sb0.10Te。
GeTe-based thermoelectric material Ge with high performance in the embodiment0.90Sb0.10The preparation method of Te comprises the following steps:
a. preparing a metal raw material vacuum tube sealing:
according to the prepared target thermoelectric material Ge0.90Sb0.10Proportioning raw materials according to a chemical formula of Te, weighing metal simple substances Ge, Sb, Ti and Te with the purity of 99.99% according to a stoichiometric ratio respectively to serve as the proportioned raw materials, sequentially placing the raw materials of each component in a clean quartz tube, and performing vacuum sealing through a vacuum tube sealing machine for later use;
b. melting and quenching treatment of metal raw materials:
b, placing the well-sealed quartz tube filled with the raw material metal material prepared in the step a into a muffle furnace for melting reaction, heating the quartz tube filled with the raw material to 950 ℃ at the speed of 120 ℃/h, preserving heat for 24h to enable the raw material to fully react in a molten state, and then quenching in cold water to obtain a quenched ingot;
c. and (3) ingot casting diffusion annealing treatment:
b, vacuum sealing the ingot after quenching treatment in the step b in a quartz tube, placing the sealed quartz tube in an annealing furnace, heating the quartz tube filled with the ingot to 700 ℃ at the speed of 120 ℃/h, preserving heat for 3 days, performing high-temperature diffusion annealing, and then slowly cooling to room temperature to obtain a GeTe annealed ingot;
SPS sintering:
grinding the GeTe cast ingot annealed in the step c into powder in an agate mortar, placing the powder in a graphite mold, performing discharge plasma sintering in a vacuum environment, heating to 500 ℃ at a speed of 100 ℃/min, adjusting the pressure to 50Mpa, keeping the temperature and the pressure for 5min, performing discharge plasma sintering, and cooling to room temperature to obtain high-performance Ge0.90Sb0.10Te bulk thermoelectric material.
Example two:
this embodiment is substantially the same as the first embodiment, and is characterized in that:
in this embodiment, a high performance GeTe based thermoelectric material has a chemical formula of Ge0.89Ti0.01Sb0.10Te。
GeTe-based thermoelectric material Ge with high performance in the embodiment0.89Ti0.01Sb0.10The preparation method of Te comprises the following steps:
a. preparing a metal raw material vacuum tube sealing:
according to the prepared target thermoelectric material Ge0.89Ti0.01Sb0.10Proportioning raw materials according to a chemical formula of Te, weighing metal simple substances Ge, Sb, Ti and Te with the purity of 99.99% according to a stoichiometric ratio respectively to serve as the proportioned raw materials, sequentially placing the raw materials of each component in a clean quartz tube, and performing vacuum sealing through a vacuum tube sealing machine for later use;
b. melting and quenching treatment of metal raw materials: the step is the same as the first embodiment;
c. and (3) ingot casting diffusion annealing treatment: the step is the same as the first embodiment;
SPS sintering:
grinding the GeTe cast ingot annealed in the step c into powder in an agate mortar, placing the powder in a graphite mold, performing discharge plasma sintering in a vacuum environment, heating to 500 ℃ at a speed of 100 ℃/min, adjusting the pressure to 50Mpa, keeping the temperature and the pressure for 5min, and placingElectro-plasma sintering followed by cooling to room temperature to obtain high performance Ge0.89Ti0.01Sb0.10Te bulk thermoelectric material.
Example three:
this embodiment is substantially the same as the previous embodiment, and is characterized in that:
in this embodiment, a GeTe based thermoelectric material with pseudo-cubic phase structure has a chemical formula of Ge0.88Ti0.02Sb0.10Te。
GeTe-based thermoelectric material Ge with pseudo-cubic phase structure in the embodiment0.88Ti0.02Sb0.10The preparation method of Te comprises the following steps:
a. preparing a metal raw material vacuum tube sealing:
according to the prepared target thermoelectric material Ge0.88Ti0.02Sb0.10Proportioning raw materials according to a chemical formula of Te, weighing metal simple substances Ge, Sb, Ti and Te with the purity of 99.99% according to a stoichiometric ratio respectively to serve as the proportioned raw materials, sequentially placing the raw materials of each component in a clean quartz tube, and performing vacuum sealing through a vacuum tube sealing machine for later use;
b. melting and quenching treatment of metal raw materials: the step is the same as the first embodiment;
c. and (3) ingot casting diffusion annealing treatment: the step is the same as the first embodiment;
SPS sintering:
grinding the GeTe cast ingot annealed in the step c into powder in an agate mortar, placing the powder in a graphite mold, performing discharge plasma sintering in a vacuum environment, heating to 500 ℃ at a speed of 100 ℃/min, adjusting the pressure to 50Mpa, keeping the temperature and the pressure for 5min, performing discharge plasma sintering, and cooling to room temperature to obtain Ge with a pseudo-cubic phase structure0.88Ti0.02Sb0.10Te bulk thermoelectric material.
Example four:
this embodiment is substantially the same as the previous embodiment, and is characterized in that:
in the present embodiment, a pseudo cubic phase structure GeTe based thermoelectric material of the formula Ge0.87Ti0.03Sb0.10Te。
GeTe-based thermoelectric material Ge with pseudo-cubic phase structure in the embodiment0.87Ti0.03Sb0.10The preparation method of Te comprises the following steps:
a. preparing a metal raw material vacuum tube sealing:
according to the prepared target thermoelectric material Ge0.87Ti0.03Sb0.10Proportioning raw materials according to a chemical formula of Te, weighing metal simple substances Ge, Sb, Ti and Te with the purity of 99.99% according to a stoichiometric ratio respectively to serve as the proportioned raw materials, sequentially placing the raw materials of each component in a clean quartz tube, and performing vacuum sealing through a vacuum tube sealing machine for later use;
b. melting and quenching treatment of metal raw materials: the step is the same as the first embodiment;
c. and (3) ingot casting diffusion annealing treatment: the step is the same as the first embodiment;
SPS sintering:
grinding the GeTe cast ingot annealed in the step c into powder in an agate mortar, placing the powder in a graphite mold, performing discharge plasma sintering in a vacuum environment, heating to 500 ℃ at a speed of 100 ℃/min, adjusting the pressure to 50Mpa, keeping the temperature and the pressure for 5min, performing discharge plasma sintering, and cooling to room temperature to obtain Ge with a pseudo-cubic phase structure0.87Ti0.03Sb0.10Te bulk thermoelectric material.
In view of the above embodiments, the GeTe based thermoelectric material having a pseudo cubic phase structure according to the above embodiments has a chemical formula of Ge0.90-xTixSb0.10Te, wherein the value of x is divided into 0, 0.01, 0.02 and 0.03.
Experimental test analysis:
example Ge0.90-xTixSb0.10Te thermoelectric material as a test sample, performance test and characterization, Ge prepared in the above example0.90-xTixSb0.10The X-ray diffraction pattern of the Te thermoelectric material is shown in FIG. 1, wherein X-rayThe line diffraction pattern shows that the crystal structure of the sample gradually changes from a rhombohedral phase structure to a pseudo-cubic phase structure with the increase of the Ti doping content.
Ge0.90-xTixSb0.10The relation of the electric conductivity of the Te thermoelectric material along with the temperature is shown in a figure 2, the curve of the electric conductivity of a sample along with the temperature has an inflection point, which is caused by the phase change of the sample, and the electric conductivity of the material is reduced along with the increase of the doping content of Ti under the same temperature. Ge (germanium) oxide0.90-xTixSb0.10The relation of the Seebeck coefficient of the Te thermoelectric material with the temperature is shown in figure 3, the curve of the Seebeck coefficient with the temperature of a sample also has an inflection point, which is consistent with the change of the electric conductivity, and the Seebeck coefficient of the material is increased along with the increase of the doping content of Ti under the same temperature. FIG. 4 is Ge0.90-xTixSb0.10The Seebeck coefficient of Te thermoelectric material is plotted against the carrier concentration, indicating that0.88Ti0.02Sb0.10Te and Ge0.87Ti0.03Sb0.10In Te, the effective mass and the density of states are improved because of the high symmetry and the greater energy band degeneracy of cubic phase GeTe, which results in higher density of states and effective mass, which results in Ge0.88Ti0.02Sb0.10Te and Ge0.87Ti0.03Sb0.10The Seebeck coefficient in Te is higher.
FIG. 5 is Ge0.90-xTixSb0.10The relation diagram of the total thermal conductivity and the temperature change of the Te thermoelectric material is shown, the thermal conductivity of the sample does not change remarkably with the temperature, the total thermal conductivity is remarkably reduced after Ti element is doped, and Ge is0.90-xTixSb0.10The lattice thermal conductivity of Te thermoelectric materials is related to temperature change as shown in fig. 6, the low lattice thermal conductivity should be attributed to strong scattering of phonons by various nanostructures and defects, and the Ti, Sb and Ge atomic radii and mass differences cause larger mass and strain fluctuations than GeTe doped with Sb alone, and also contribute to reducing the lattice thermal conductivity.
FIG. 7 is Ge0.90-xTixSb0.10Dimensionless figure of merit, zT, and temperature variation for Te thermoelectric materialsThe comparison shows that when x is 0.02, the electrical property optimization and the reduction of the lattice thermal conductivity result in high thermoelectric property, the thermoelectric figure of merit of the GeTe-based thermoelectric material is as high as 1.9, and the crystal structure at room temperature is stable pseudo-cubic phase.
In summary, the chemical formula of the pseudo cubic phase GeTe based thermoelectric material of the above embodiments of the invention is Ge0.90- xTixSb0.10Te, wherein the value range of x is more than or equal to 0 and less than or equal to 0.03. The GeTe based thermoelectric material with the pseudo-cubic phase structure in the embodiment of the invention is lead-free, has a stable pseudo-cubic phase structure at room temperature, has lower thermal conductivity and has good thermoelectric performance in a working temperature range.
Example five:
this embodiment is substantially the same as the previous embodiment, and is characterized in that:
in this embodiment, a GeTe based thermoelectric material with pseudo-cubic phase structure has a chemical formula of Ge0.88Ti0.02Sb0.10Te。
GeTe-based thermoelectric material Ge with pseudo-cubic phase structure in the embodiment0.88Ti0.02Sb0.10The preparation method of Te comprises the following steps:
a. preparing a metal raw material vacuum tube sealing:
according to the prepared target thermoelectric material Ge0.88Ti0.02Sb0.10Proportioning raw materials according to a chemical formula of Te, weighing metal simple substances Ge, Sb, Ti and Te with the purity of 99.99% according to a stoichiometric ratio respectively to serve as the proportioned raw materials, sequentially placing the raw materials of each component in a clean quartz tube, and performing vacuum sealing through a vacuum tube sealing machine for later use;
b. melting and quenching treatment of metal raw materials:
b, placing the well-sealed quartz tube filled with the raw material metal material prepared in the step a into a muffle furnace for melting reaction, heating the quartz tube filled with the raw material to 1000 ℃ at the speed of 150 ℃/h, preserving heat for 48h to enable the raw material to fully react in a molten state, and then quenching in cold water to obtain a quenched ingot;
c. and (3) ingot casting diffusion annealing treatment:
b, vacuum sealing the ingot after quenching treatment in the step b in a quartz tube, placing the sealed quartz tube in an annealing furnace, heating the quartz tube filled with the ingot to 600 ℃ at the speed of 150 ℃/h, preserving the heat for 4 days, performing high-temperature diffusion annealing, and then slowly cooling to room temperature to obtain a GeTe annealed ingot;
SPS sintering:
grinding the GeTe cast ingot annealed in the step c into powder in an agate mortar, placing the powder in a graphite mold, performing discharge plasma sintering in a vacuum environment, heating to 550 ℃ at the speed of 200 ℃/min, adjusting the pressure to 60Mpa, keeping the temperature and the pressure for 5min, performing discharge plasma sintering, and cooling to room temperature to obtain Ge with a pseudo-cubic phase structure0.88Ti0.02Sb0.10Te bulk thermoelectric material.
Experimental test analysis:
the GeTe-based thermoelectric material Ge with the pseudo-cubic phase structure is prepared by adopting the embodiment0.88Ti0.02Sb0.10And Te is taken as a sample, performance test and characterization are carried out, and the diffraction experiment test shows that the crystal structure of the sample is gradually changed from a rhombohedral phase structure to a pseudo-cubic phase structure. This example pseudo-cubic Ge0.88Ti0.02Sb0.10In Te, the effective mass and the density of states are improved because of the high symmetry and the larger energy band degeneracy of cubic phase GeTe, which leads to the higher density of states and effective mass, and leads to the Ge of the embodiment0.88Ti0.02Sb0.10The Seebeck coefficient in Te is higher. The pseudo cubic phase structure Ge of the embodiment0.88Ti0.02Sb0.10The Te thermoelectric material is lead-free, has a stable pseudo-cubic phase structure at room temperature, has lower thermal conductivity and has good thermoelectric performance within a working temperature range.
While the embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to the above embodiments, but various changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the present invention should be made in equivalent substitution ways, so long as the object of the present invention is met, and the present invention is within the protection scope of the present invention without departing from the technical principle and inventive concept of the pseudo cubic phase structure GeTe based thermoelectric material and the method for manufacturing the same.
Claims (10)
1. A pseudo cubic phase structure GeTe-based thermoelectric material is characterized in that: having the chemical formula Ge0.90-xTixSb0.10Te, wherein the value range of x is more than or equal to 0 and less than or equal to 0.03.
2. The pseudo-cubic phase structured GeTe-based thermoelectric material according to claim 1, wherein: the value range of x is more than or equal to 0.01 and less than or equal to 0.03.
3. The pseudo-cubic phase structured GeTe-based thermoelectric material according to claim 2, wherein: the value of x is 0.02.
4. A method for preparing a pseudo cubic phase structured GeTe-based thermoelectric material as claimed in claim 1, comprising the steps of:
a. preparing a metal raw material vacuum tube sealing:
according to the numerical value of x of the chemical formula of the prepared target thermoelectric material, respectively weighing the metal simple substances Ge, Sb, Ti and Te with the purity of not less than 99.99% according to the stoichiometric ratio, sequentially placing the raw materials of each component in a clean quartz tube, and performing vacuum sealing through a vacuum tube sealing machine for later use;
b. melting and quenching treatment of metal raw materials:
heating the well-sealed quartz tube filled with the raw material metal material prepared in the step a to melt and react the raw material, and then quenching in cold water to obtain a quenched ingot;
c. and (3) ingot casting diffusion annealing treatment:
sealing the ingot subjected to quenching treatment in the step b in a quartz tube in vacuum, annealing at high temperature, and then slowly cooling to room temperature to obtain an annealed ingot;
SPS sintering:
and c, grinding the ingot after annealing treatment in the step c into powder, placing the powder in a graphite mold, performing discharge plasma sintering, and cooling to room temperature to obtain the bulk GeTe-based thermoelectric material with the pseudo-cubic phase structure.
5. The method for producing a pseudo cubic phase structured GeTe based thermoelectric material as claimed in claim 4, wherein: in the step b, the quartz tube filled with the raw materials is heated to 900-1000 ℃ at the speed of 100-150 ℃/h, and the temperature is kept for 1-2 days, so that the raw materials are fully reacted in a molten state.
6. The method for producing a pseudo-cubic-phase-structure GeTe-based thermoelectric material as claimed in claim 5, wherein: in the step b, the quartz tube filled with the raw materials is heated to 950 ℃ at the speed of 120 ℃/h, and the temperature is kept for 24h, so that the raw materials are fully reacted in a molten state.
7. The method for producing a pseudo cubic phase structured GeTe based thermoelectric material as claimed in claim 4, wherein: in the step c, heating the quartz tube with the ingot to 600-700 ℃ at the speed of 100-150 ℃/h, preserving the heat for 2-4 days, and performing high-temperature diffusion annealing.
8. The method for producing a pseudo-cubic-phase-structure GeTe-based thermoelectric material as claimed in claim 7, wherein: in the step c, the quartz tube with the ingot is heated to 700 ℃ at the speed of 120 ℃/h, and is kept warm for 3 days, and high-temperature diffusion annealing is carried out.
9. The method for producing a pseudo cubic phase structured GeTe based thermoelectric material as claimed in claim 4, wherein: in the step d, the temperature is increased to 500-550 ℃ at the speed of 100-200 ℃/min, the pressure is adjusted to 50-60 Mpa, the temperature is kept at constant temperature and constant pressure for at least 5min, and the spark plasma sintering is carried out.
10. The method for producing a pseudo-cubic-phase-structure GeTe-based thermoelectric material as claimed in claim 9, wherein: in the step d, the temperature is increased to 500 ℃ at the speed of 100 ℃/min, the pressure is adjusted to 50Mpa, and the sintering is carried out by discharging plasma under the constant temperature and pressure for 5 min.
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