Preparation method of high-performance GeTe thermoelectric material

Abstract

The application belongs to the field of materials, and discloses a preparation method of high-performance GeTe thermoelectric material, Ge powder, Zr powder, Pb powder, Te powder and Cu2Te powder are respectively taken according to the molar ratio of 0.965-x:0.02:x:0.985:0.015, wherein the value of x is respectively 0, 0.06 and 0.08, then the powders are loaded into a quartz tube for vacuum sealing, and are sequentially subjected to sintering in a box furnace, cold water quenching, annealing in a box furnace, cold water quenching and sintering in a rapid hot-pressing furnace, so as to obtain Zr, Cu2Te and Pb co-doped high-performance GeTe thermoelectric material. The method has simple preparation process, high operability and high repeatability, and the prepared GeTe doped with Zr, Cu2Te and Pb compound has the characteristics of high crystallinity and high density. The method can greatly improve the thermoelectric figure of merit of GeTe thermoelectric material, and the thermoelectric figure of merit is at a high level in the thermoelectric report, so the method has good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of thermoelectric materials, and relates to a preparation method of high-performance GeTe thermoelectric material. BACKGROUND

[0002] Since the industrial revolution, the vigorous development of the economic society is inseparable from the increasing consumption of energy, which leads to the major problem of energy shortage and further hinders the sustainable development of human society. On the one hand, traditional fossil energy is a non-renewable resource, and people increase the mining intensity of resources such as coal, oil and natural gas, which causes such resources to face the problem of exhaustion, and at the same time, people also pollute the environment in the process of using resources. On the other hand, with the development of human society, the total population of the world is increasing day by day, and people's demand for fossil energy is increasing, which will inevitably exacerbate the phenomenon of energy shortage and environmental pollution. Therefore, how to improve the problem of world energy shortage and environmental deterioration has become the focus and central topic of attention of various countries.

[0003] Thermoelectric materials are a kind of functional materials that can directly realize the mutual conversion of heat energy and electric energy through temperature difference, and have the characteristics of small volume, high reliability, wide applicable temperature range, environmental friendliness and the like. At present, this thermoelectric technology has been successfully applied to deep space probes with thermoelectric devices using radioactive isotope radiation heat and small nuclear reactor heat as the only power supply system. In addition, thermoelectric materials also show potential value and broad prospects in the fields of industrial waste heat recovery, hydrocarbon fuel thermoelectric power generation and solar photovoltaic-thermoelectric hybrid power generation, which has strong practical significance for solving the energy crisis and environmental pollution.

[0004] The performance of thermoelectric materials is mainly measured by the dimensionless thermoelectric figure of merit (ZT value), and its expression is: ZT = S2 T (S 2 σ / κ), wherein S、 σ , κ respectively represent Seebeck coefficient, electrical conductivity and thermal conductivity. How to obtain excellent electrical conductivity and large Seebeck coefficient, and effectively reduce the thermal conductivity to obtain as high ZT value as possible is the core content of the research in the field of thermoelectricity. However, S、 σ , κ three parameters are often coupled due to the close relationship with carrier concentration, which often leads to the general reduction of hot spot power generation efficiency. Therefore, according to the material characteristics, adjusting the thermoelectric transport properties is a great challenge to obtain high thermoelectric figure of merit.

[0005] The high thermoelectric performance of p-type GeTe is well known, which has outstanding high ZT value compared with other thermoelectric materials due to higher power factor and high degeneracy of the band. The Seebeck coefficient of GeTe reaches the highest at medium temperature (600-800 K), and the thermal conductivity decreases with the increase of temperature, which shows excellent p-type medium temperature thermoelectric performance. In addition, due to its unique properties, GeTe has a narrow band gap and a phase transition process, which makes it have a complex thermoelectric behavior characteristics. This provides more potential for exploring excellent composition, microstructure and preparation process to improve the GeTe-based thermoelectric figure of merit. In addition, the mechanical properties of GeTe-based thermoelectric materials are good, which meets the requirements of thermoelectric devices on mechanical properties. These characteristics make GeTe-based thermoelectric materials have become the thermoelectric materials for practical application in deep space exploration power generation. Therefore, the high performance research of GeTe-based thermoelectric materials has broad prospects and challenges. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of p-type GeTe-based thermoelectric material with simple preparation process, high thermoelectric figure of merit and can be used for thermoelectric conversion and thermoelectric mechanism research.

[0007] The specific technical scheme is:

[0008] A preparation method of high-performance GeTe thermoelectric material, comprising the following steps:

[0009] (1) Ge powder, Zr powder, Pb powder, Te powder and Cu2Te powder are weighed according to the molar ratio of 0.965-x:0.02:x:0.985:0.015, wherein x is in the range of 0.04-0.12; the raw materials weighed according to the strict proportion are sequentially loaded into a washed Φ=20 mm quartz tube;

[0010] (2) the quartz tube is pumped to low vacuum degree by using a mechanical pump, and then pumped to 10 -3 Pa by using a molecular pump, and the tube is sealed by using a high-temperature flame of a hydrogen-oxygen generator;

[0011] (3) the quartz tube loaded with sample powder is placed in a high-temperature box furnace for first sintering;

[0012] (4) first sintering temperature rising: from room temperature to 950℃ for 360-720 min, and then the quartz tube is quickly taken out and quenched in cold water or ice water;

[0013] (5) the quenched quartz tube is placed in a box furnace for annealing, and the temperature rising process is: from room temperature to 600-700℃ for 180-360 min, and then quenched in cold water or ice water for 4320 min;

[0014] (6) The sintered ingot is taken out and ground in an agate mortar for 30 min, and then the sample is passed through a 300-mesh sieve to obtain a sample powder with uniform particle size;

[0015] (7) The uniform powder is loaded into a graphite mold with a diameter Φ=12.7 mm, and a rapid heat pressing furnace is used to heat the sample from room temperature to 550°C under a pressure of 55 MPa for 2-8 min, and then the sample is cooled to room temperature under no pressure.

[0016] The purity of each element raw material used in the application is 99.99%-99.999%.

[0017] Preferably, the heating time in step (4) is 720 min, and the heating time in step (5) is 210 min.

[0018] The heating time in step (7) is 3 min.

[0019] The holding time in step (7) is 30 min.

[0020] The application provides a preparation method of a high-performance GeTe thermoelectric material, which can be used for the preparation and performance improvement of GeTe doped samples, and has the characteristics of simple preparation process, good sample stability, high repeatability and the like. The method can control the phase formation degree, density and microstructure of the GeTe compound by adjusting process parameters such as heating and cooling rates, phase formation temperature, annealing temperature, hot-pressing pressure and holding time, and has strong controllability. The prepared GeTe doped with Zr, Cu2Te and Pb has high crystallinity, high density, high power factor, low thermal conductivity and high thermoelectric performance. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 X-ray diffraction pattern (XRD) of the Zr, Cu2Te and Pb co-doped GeTe thermoelectric material obtained in the example;

[0022] Figure 2 Resistivity of the Zr, Cu2Te and Pb co-doped GeTe thermoelectric material obtained in the example;

[0023] Figure 3 Seebeck coefficient of the Zr, Cu2Te and Pb co-doped GeTe thermoelectric material obtained in the example;

[0024] Figure 4 Power factor (PF) of the Zr, Cu2Te and Pb co-doped GeTe thermoelectric material obtained in the example;

[0025] Figure 5 Thermal conductivity of the Zr, Cu2Te and Pb co-doped GeTe thermoelectric material obtained in the example;

[0026] Figure 6 ZT value of Zr, Cu2Te, Pb co-doped GeTe thermoelectric material obtained in the example. DETAILED DESCRIPTION

[0027] The specific embodiments of the present application are described in combination with examples.

[0028] (1) Ge powder, Zr powder, Pb powder, Te powder and Cu2Te powder were weighed according to the molar ratio of 0.965-x:0.02:x:0.985:0.015, wherein x was 0, 0.06 and 0.08 respectively, and the weighed raw materials were sequentially loaded into a cleaned Φ=20 mm quartz tube;

[0029] (2) The quartz tube was pumped to a low vacuum degree by using a mechanical pump, and then pumped to 10 -3 Pa by using a molecular pump, and the tube was sealed by using a high-temperature flame of a hydrogen-oxygen generator;

[0030] (3) The sealed quartz tube was placed in a high-temperature box furnace for first-time sintering;

[0031] (4) The first-time sintering temperature was raised from room temperature to 950℃ in 720 min, and then the quartz tube was taken out and quenched in cold water or ice water after being kept at 950℃ for 360 min;

[0032] (5) The quenched quartz tube was placed in a box furnace for annealing, and the temperature was raised from room temperature to 650℃ in 210 min, and then the quartz tube was kept at 650℃ for 4320 min and quenched in cold water or ice water again;

[0033] (6) The sintered ingot was ground in an agate mortar for 30 min, and then the sample was passed through a 300-mesh sieve to obtain a sample powder with uniform particle size;

[0034] (7) The uniform powder was loaded into a graphite mold with a diameter of Φ=12.7 mm, and then the temperature was raised from room temperature to 550℃ in 3 min under a pressure of 55 MPa by using a rapid hot-pressing furnace, and then the temperature was kept at 550℃ for 30 min, and then the sample was cooled to room temperature without pressure.

[0035] (8) The phase analysis of the Zr, Cu2Te, Pb co-doped GeTe thermoelectric material was performed by using an X-ray diffractometer (XRD), as shown in FIG. 1, wherein the vertical coordinate Intensity represents the intensity of the diffraction peak, and the horizontal coordinate 2θ represents the angle of the diffraction peak. Figure 1 The three samples [Ge 0.965 Zr 0.02 Te 0.985 (Cu2Te) 0.015 , Ge 0.965 Zr 0.02 Pb0.06 Te 0.985 (Cu2Te) 0.015 、Ge 0.965 Zr 0.02 Pb 0.08 Te 0.985 (Cu2Te) 0.015 All of these reflect the GeTe rhombohedral phase.

[0036] (9) The resistivity and Seebeck coefficient of the Zr, Cu2Te, and Pb co-doped GeTe thermoelectric material were measured using a thermoelectric property evaluation device (CTA-3), as shown below. Figure 2 , Figure 3 As shown, the ordinate S and T represent resistivity and Seebeck coefficient, respectively, with T representing temperature on the horizontal axis. The two samples [Ge] after doping... 0.965 Zr 0.02 Pb 0.06 Te 0.985 (Cu2Te) 0.015 、Ge 0.965 Zr 0.02 Pb 0.08 Te 0.985 (Cu2Te) 0.015 The Seebeck coefficient shows a significant overall increase, reaching a maximum of 272 mV K at 553 K. -1 Furthermore, the Seebeck coefficient is positive, indicating that all samples are p-type semiconductors.

[0037] (10) According to Figure 2 and Figure 3 The test results can be converted into the power factor (PF) of the Zr, Cu2Te, and Pb co-doped GeTe thermoelectric material, as shown in Figure 4, where the vertical axis PF represents the power factor and the horizontal axis T represents the temperature. With increasing Pb doping content, the sample [GeTe...]... 0.965 Zr 0.02 Te 0.985 (Cu2Te) 0.015 、Ge 0.965 Zr 0.02 Pb 0.06 Te 0.985 (Cu2Te) 0.015 、Ge 0.965 Zr 0.02 Pb 0.08 Te 0.985 (Cu2Te) 0.015 All of them exhibit high power factors, demonstrating superior thermoelectric properties.

[0038] (11) The thermal diffusivity of the Zr, Cu2Te, and Pb co-doped GeTe thermoelectric material was measured using a laser thermal conductivity meter (LFA-467), and then converted into thermal conductivity, such as... Figure 5 As shown, the vertical axis κ represents thermal conductivity, and the horizontal axis T represents temperature. With increasing Pb doping content, the [Ge] sample... 0.965 Zr 0.02 Te 0.985 (Cu2Te) 0.015 、Ge 0.965 Zr 0.02 Pb 0.06 Te 0.985 (Cu2Te) 0.015 、Ge 0.965 Zr 0.02 Pb 0.08 Te 0.985 (Cu2Te) 0.015 The thermal conductivity was significantly reduced, from 3.14 W / m at 303 K. -1 K -1 Reduced to 1.42 W m -1 K -1 At 603K, from 1.75 W / m -1 K -1 Reduced to 1 W m -1 K -1 .

[0039] (12) According to Figure 2 , Figure 3 , Figure 4 The test results can be converted into the dimensionless thermoelectric figure of merit (ZT value) of Zr, Cu2Te, Pb co-doped GeTe thermoelectric materials, such as... Figure 6 As shown, the vertical axis ZT represents the thermoelectric figure of merit, and the horizontal axis T represents the temperature. The three doped samples [Ge]... 0.965 Zr 0.02 Te 0.985 (Cu2Te) 0.015 、Ge 0.965 Zr 0.02 Pb 0.06 Te 0.985 (Cu2Te) 0.015 、Ge 0.965 Zr 0.02 Pb 0.08 Te 0.985 (Cu2Te) 0.015 The thermoelectric figure of merit of Ge shows a gradual improvement, with the value increasing at 653 K. 0.965 Zr 0.02 Pb 0.08 Te 0.985 (Cu2Te)0.015 thermoelectric figure of merit compared to Ge 0.985 Te 0.985 (Cu2Te) 0.015 With a significant increase of approximately 180%, it can reach 2.14, thus having a strong application prospect.

Claims

1. A method for preparing a high-performance GeTe thermoelectric material, characterized by, The method comprises the following steps: (1) Ge powder, Zr powder, Pb powder, Te powder and Cu2Te powder are weighed according to the molar ratio of 0.965-x:0.02:x:0.985:0.015, wherein x ranges from 0.04 to 0.12; the raw materials weighed according to the ratio are sequentially loaded into a washed Φ=20 mm quartz tube; (2) The quartz tube is pumped to low vacuum degree by mechanical pump, and then to 10 -3 Pa by molecular pump, and the tube is sealed by high temperature flame of hydrogen-oxygen generator (3) the quartz tube containing the sample powder is placed in a high-temperature box furnace for first-time sintering; (4) after the first-time sintering is completed, the quartz tube is quickly taken out and quenched in cold water; (5) then, the quenched quartz tube is placed in a box furnace for annealing, and quenched in cold water again; (6) the sintered ingot is ground in an agate mortar for 30 min, and the sample is passed through a 300-mesh screen to obtain sample powder with uniform particle size; (7) the uniform powder is loaded into a graphite mold with a diameter of Φ=12.7 mm, and then densification sintering is performed by using a rapid hot-pressing furnace.

2. The method of claim 1, wherein the GeTe thermoelectric material has a figure of merit ZT of at least 0.5 at 800 K. In step (3), the first-time sintering has the following temperature rising process: from room temperature to 950 DEG C in 360-720 min, and holding for 360 min.

3. The method of claim 1, wherein the GeTe thermoelectric material has a figure of merit ZT of 0.5 or more at 800 K. In step (5), the annealing has the following temperature rising process: from room temperature to 600-700 DEG C in 180-360 min, and holding for 4320 min.

4. The method of claim 1, wherein the GeTe thermoelectric material has a figure of merit (ZT) of at least 0.5 at 800 K. In steps (4) and (5), the cold water quenching has the following operation process: the quartz tube is quickly taken out from the high-temperature box furnace, and then placed in cold water or ice water to cool down.

5. The method of claim 1, wherein the GeTe thermoelectric material has a figure of merit (ZT) of at least 0.5 at 800 K. In step (7), the rapid hot-pressing furnace densification sintering has the following program: from room temperature to 550 DEG C in 2-8 min under a pressure of 55 MPa, and holding for 30-45 min; then, air cooling to room temperature without pressure.

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