CuInTe2-based thermoelectric semiconductor crystal and preparation method thereof

Abstract

The invention provides a CuInTe2-based thermoelectric semiconductor crystal and a preparation method thereof, and belongs to the field of semiconductor crystals. The raw materials of the CuInTe2-based thermoelectric semiconductor crystal comprise elementary substance Cu, elementary substance In and elementary substance Te, and the molar ratio of the elementary substance Cu to the elementary substance In to the elementary substance Te is 1: (0.8-1.2): (2-2.2). The CuInTe2-based thermoelectric semiconductor crystal is obtained by mixing and melting elementary substance Cu, elementary substance In and elementary substance Te, carrying out melt growth from top to bottom and adding or not adding seed crystals in the crystal growth process. The thermoelectric performance of the CuInTe2-based thermoelectric semiconductor crystal is improved and the power factor and Seebeck coefficient at room temperature are improved by regulating and controlling the molar ratio of the raw material simple substances and controlling the vertical melting growth condition, and the power factor and Seebeck coefficient are obviously higher than those of CuInTe2-based polycrystal.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of semiconductor crystals, and particularly relates to a CuInTe2-based thermoelectric semiconductor crystal and a preparation method thereof. BACKGROUND

[0002] Thermoelectric materials have the characteristics of mutual conversion between thermal energy and electrical energy, and are widely concerned in energy development and utilization. The ternary chalcopyrite compound CuInTe2 is a p-type thermoelectric material in the medium temperature range, has high stability, and has a tetragonal crystal structure. However, the crystal structure of CuInTe2-based materials is ordered, the covalent bond force is strong, and the thermal conductivity is high. In addition, CuInTe2-based materials are p-type thermoelectric materials with a medium band gap, and the thermal excitation carrier concentration at room temperature is significantly lower than the preferred value of thermoelectric materials, and the carrier mobility is low, resulting in a low power factor, which affects the thermoelectric conversion performance.

[0003] In existing research, in order to improve the thermoelectric performance of CuInTe2, increase the hole concentration and reduce the thermal conductivity, Yubo Luo et al. (Nano Energy, 2015, 18, 37-46) proposed a method of combining point defects and microstructure engineering to optimize the thermoelectric performance of CuInTe2. By introducing a large number of ZnTe point defects into the CuInTe2 matrix, a (CuInTe2) 1-x (2ZnTe) x solid solution was obtained, the order of carrier concentration was improved, the power factor was significantly enhanced, and titanium dioxide powder was added to reduce the thermal conductivity. The existing technology mainly introduces other hole carriers through element doping or nanocomposite to improve the performance of thermoelectric materials, but there are problems such as introduction of impurities, high interface thermal resistance, and low carrier mobility. The application is different from the doping of other elements, and the intrinsic defects are adjusted to change the lattice order, control the phonon transport and carrier concentration, reduce the thermal conductivity, and improve the power factor. SUMMARY

[0004] In view of the problems still existing in the prior art, the application provides a CuInTe2-based thermoelectric semiconductor crystal and a preparation method thereof. The purpose of the application is to solve the problems of weak high-lattice-phonon scattering, low carrier concentration and low mobility by regulating the molar ratio of elemental Cu, elemental In and elemental Te and utilizing intrinsic defects. Another purpose of the application is to solve the problem of low power factor of CuInTe2-based polycrystal at room temperature by significantly improving the power factor and the Seebeck coefficient of CuInTe2-based thermoelectric semiconductor crystal at room temperature. A further purpose of the application is to solve the problem of random crystal orientation and / or defect distribution by regulating the ratio of each raw material element and controlling the regional temperature under the action of vertical melt growth, thereby obtaining a large-size CuInTe2-based thermoelectric semiconductor crystal.

[0005] To achieve the above-mentioned purposes, the application adopts the following technical solutions. In one aspect, the application provides a CuInTe2-based thermoelectric semiconductor crystal, and the raw materials include elemental Cu, elemental In and elemental Te. The molar ratio of the elemental Cu, the elemental In and the elemental Te is 1:(0.8-1.2):(2-2.2).

[0006] The application regulates the molar ratio of the elemental Cu, the elemental In and the elemental Te in the raw materials, changes the electron acceptor in the case of In deficiency or In enrichment or Te enrichment, provides hole carriers by utilizing intrinsic defects, solves the problem of low intrinsic carrier concentration, can cause changes in the crystal lattice structure, changes the size or mass or stress field, and can further enhance phonon scattering when Te is excessive and can be precipitated as a second phase, solves the problems of high order of crystal lattice structure and weak phonon scattering, realizes the improvement of electrical conductivity, the Seebeck coefficient and the power factor, the reduction of thermal conductivity, and the fact that the power factor and the Seebeck coefficient of the CuInTe2-based thermoelectric semiconductor crystal at room temperature are obviously higher than those of the CuInTe2-based polycrystal.

[0007] Preferably, the power factor of the CuInTe2-based thermoelectric semiconductor crystal at 300-800K is 6.8-14.8μWcm -1 K -2 .

[0008] Preferably, the Seebeck coefficient of the CuInTe2-based thermoelectric semiconductor crystal at 300-800K is 275-390μVK -1 .

[0009] Preferably, the thermal conductivity of the CuInTe2-based thermoelectric semiconductor crystal at 300-800K is 0.7-5.5Wm -1 K -1 .

[0010] As preferred, the CuInTe2-based thermoelectric semiconductor crystal has an electrical conductivity of 0.02*10 5 -0.17*10 5 S m -1 .

[0011] As preferred, the CuInTe2-based thermoelectric semiconductor crystal has a diameter of 10-40 mm and a length of 10-100 mm.

[0012] As preferred, the CuInTe2-based thermoelectric semiconductor crystal has a diameter of 15-40 mm.

[0013] In another aspect, the present application provides a preparation method of the CuInTe2-based thermoelectric semiconductor crystal as above, comprising the following steps: S1: mixing and melting elemental Cu, elemental In and elemental Te, and obtaining CuInTe2-based polycrystal after cooling; S2: melt-growth of the CuInTe2-based polycrystal from top to bottom, with or without adding seed crystal during the crystal growth, to obtain the CuInTe2-based thermoelectric semiconductor crystal.

[0014] As preferred, in the S1, the elemental Cu, elemental In and elemental Te are mixed and vacuum-sealed in a quartz crucible with a conical bottom and a taper of 18-44°, at a vacuum degree of 10 -2 -10 -3 Pa, and then loaded into a vertical melting furnace or a rocking furnace for melting, at a melting temperature of 1000-1100℃ and a heating rate of 2-10℃ / min, and cooled after melting to obtain the CuInTe2-based polycrystal; the rocking furnace has a rocking rate of 10-30 r / min and a rocking time of 0.5-3 h.

[0015] As preferred, in the S2, the melt-growth is carried out in a vertical growth furnace in sections: the temperature of the melting section is 1000-1100℃, and the residence time is 8-18 h; the temperature of the crystal growth section is 650-950℃, and the temperature decreasing rate from top to bottom is 5-15℃ / cm, and the crystal growth rate is 0.5-2 mm / h; the temperature of the annealing section is 300-500℃, and the annealing time is 8-10 h.

[0016] As preferred, in the S2, no seed crystal is added during the crystal growth.

[0017] The application obtains large-size CuInTe2-based thermoelectric semiconductor crystals by top-to-bottom melt growth on the basis of regulating the proportion of each raw material element, guiding the crystal orientation, and can select to add or not to add seed crystals during the crystal growth process, the addition of seed crystals can be used as a crystal orientation template to limit the growth direction, and the regional temperature is regulated to avoid the problems of random nucleation and instability of the seed crystal and melt interface; without adding seed crystals can promote the uniform distribution of intrinsic defects, enhance phonon scattering, and avoid the problems of introducing impurities or dislocations. The crystal is controlled by partition temperature during the melt growth process, which can ensure the directional melt solidification, and ensure the growth quality of the crystal during the temperature decrease process, avoid the problems of temperature sudden change affecting the melt flow and stability, and reducing the uniformity of intrinsic defect distribution, further promote the CuInTe2-based thermoelectric semiconductor crystals to have higher power factor and Seebeck coefficient at room temperature.

[0018] Compared with the prior art, the application has the following beneficial effects: The application can effectively reduce the thermal conductivity, improve the power factor, electrical conductivity and Seebeck coefficient in the case of In-poor or In-rich or Te-rich. The application can use seed crystals as a crystal orientation template during the crystal growth process, and regulate the regional temperature to limit the growth direction without affecting the stability of the seed crystal and the melt interface. The application can promote the uniform distribution of intrinsic defects without introducing impurities or causing dislocations by not adding seed crystals during the crystal growth process. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The X-ray diffraction pattern of the CuInTe2 crystal in Example 2.

[0020] Figure 2 The element distribution face scanning spectrum of the CuInTe2 crystal in Example 2. DETAILED DESCRIPTION

[0021] The application will be further described in detail below in combination with specific embodiments, and the examples given are only for illustrating the application, not for limiting the scope of the application.

[0022] OVERALL EXAMPLE A preparation method of a CuInTe2-based thermoelectric semiconductor crystal, comprising the following steps: S1: raw material elements Cu, In and Te are mixed and melted according to a molar ratio of 1: (0.8-1.2): (2-2.2), vacuum sealed in a quartz crucible with a conical bottom and a taper of 18-44°, and the vacuum degree is 10 -2 -10 -3Pa, and the CuInTe2-based polycrystal is obtained by cooling after melting in a rocking furnace, wherein the rocking rate of the rocking furnace is 10-30 r / min, the rocking time is 0.5-3 h, the melting temperature is 1000-1100 DEG C, the temperature rising speed is 2-10 DEG C / min. S2: the CuInTe2-based polycrystal is subjected to vertical growth and melting growth in a vertical growth furnace from top to bottom, and the temperature of the melting zone is 1000-1100 DEG C, and the residence time is 8-18 h; the temperature of the crystal growth zone is 650-950 DEG C, and the temperature decreasing speed from top to bottom is 5-15 DEG C / cm, and the crystal growth speed is 0.5-2 mm / h; the temperature of the annealing zone is 300-500 DEG C, and the annealing time is 8-10 h; seed crystal is added or not added during the crystal growth process, and finally the CuInTe2-based thermoelectric semiconductor crystal with a diameter of 10-40 mm (preferably 15-40 mm) and a length of 10-100 mm is obtained.

[0023] The CuInTe2-based thermoelectric semiconductor crystal prepared by the method has high power factor, Seebeck coefficient and electrical conductivity, and low thermal conductivity; the power factor can reach 13 muWcm -1 K -2 The Seebeck coefficient can reach 390 muVK -1 at room temperature, which are significantly higher than those of the CuInTe2-based polycrystal; the thermal conductivity is 0.7-6.7 Wm -1 K -1 The temperature of each zone is controlled during the vertical melting growth process, random nucleation and unstable seed crystal and melt interface are avoided, directional melting and solidification are promoted, and the growth quality of the crystal is ensured during the temperature decreasing process, and the size of the crystal is increased.

[0024] Example 1 A preparation method of a CuInTe2-based thermoelectric semiconductor crystal, comprising the following steps: S1: raw material elements Cu, In and Te are mixed and melted according to a molar ratio of 1:0.8:2.1, and then the mixture is vacuum sealed in a quartz crucible with a conical bottom and a taper of 30 DEG, wherein the vacuum degree is 10 -3 Pa, and the CuInTe2-based polycrystal is obtained by cooling after melting in a rocking furnace, wherein the rocking rate of the rocking furnace is 20 r / min, the rocking time is 1 h, the melting temperature is 1000 DEG C, the temperature rising speed is 4 DEG C / min. S2: melt-growth the CuInTe2-based polycrystal from top to bottom in a vertical growth furnace, which is carried out in sections, in order: the temperature of the melting zone is 1000℃, the residence time is 12h; the temperature of the crystal growth zone is 800℃, the temperature decreasing speed from top to bottom is 5℃ / cm, the crystal growth speed is 2mm / h; the temperature of the annealing zone is 500℃, the annealing time is 10h; no seed crystal is added during the crystal growth process, and finally a CuInTe2-based thermoelectric semiconductor crystal with a diameter of 30mm and a length of 100mm is obtained.

[0025] Example 2 A preparation method of a CuInTe2-based thermoelectric semiconductor crystal, comprising the following steps: S1: melt the raw material elements Cu, In and Te in a molar ratio of 1:0.9:2.1, vacuum seal them in a quartz crucible with a conical bottom and a taper of 30°, and vacuumize them to a vacuum degree of 10 -3 Pa, melt them in a rocking furnace, the rocking speed of the rocking furnace is 20r / min, the rocking time is 1h, the melting temperature is 1000℃, the temperature rising speed is 4℃ / min, and after melting, cool to obtain CuInTe2-based polycrystal; S2: melt-growth the CuInTe2-based polycrystal from top to bottom in a vertical growth furnace, which is carried out in sections, in order: the temperature of the melting zone is 1000℃, the residence time is 12h; the temperature of the crystal growth zone is 800℃, the temperature decreasing speed from top to bottom is 5℃ / cm, the crystal growth speed is 2mm / h; the temperature of the annealing zone is 500℃, the annealing time is 10h; no seed crystal is added during the crystal growth process, and finally a CuInTe2-based thermoelectric semiconductor crystal with a diameter of 30mm and a length of 100mm is obtained.

[0026] Example 3 A preparation method of a CuInTe2-based thermoelectric semiconductor crystal, comprising the following steps: S1: melt the raw material elements Cu, In and Te in a molar ratio of 1:0.8:2.2, vacuum seal them in a quartz crucible with a conical bottom and a taper of 30°, and vacuumize them to a vacuum degree of 10 -3 Pa, melt them in a rocking furnace, the rocking speed of the rocking furnace is 30r / min, the rocking time is 2h, the melting temperature is 1050℃, the temperature rising speed is 2℃ / min, and after melting, cool to obtain CuInTe2-based polycrystal; S2: melt-growth the CuInTe2-based polycrystal from top to bottom in a vertical growth furnace, which is carried out in sections, in order: the temperature of the melting zone is 1050℃, the residence time is 14h; the temperature of the crystal growth zone is 750℃, the temperature decreasing speed from top to bottom is 5℃ / cm, the crystal growth speed is 1.5mm / h; the temperature of the annealing zone is 400℃, the annealing time is 9h; seed crystal is added during the crystal growth process, and finally a CuInTe2-based thermoelectric semiconductor crystal with a diameter of 30mm and a length of 100mm is obtained.

[0027] Example 4 A preparation method of a CuInTe2-based thermoelectric semiconductor crystal, comprising the following steps: S1: melt the raw material elements Cu, In and Te in a molar ratio of 1:0.9:2.2, vacuum seal them in a quartz crucible with a conical bottom and a taper of 30°, and vacuumize to a degree of 10 -3 Pa, melt them in a rocking furnace, the rocking speed of the rocking furnace is 30r / min, the rocking time is 2h, the melting temperature is 1050℃, the heating speed is 2℃ / min, and after melting, cool to obtain CuInTe2-based polycrystal; S2: melt-growth the CuInTe2-based polycrystal from top to bottom in a vertical growth furnace, which is carried out in sections, in order: the temperature of the melting zone is 1050℃, the residence time is 14h; the temperature of the crystal growth zone is 750℃, the temperature decreasing speed from top to bottom is 5℃ / cm, the crystal growth speed is 1.5mm / h; the temperature of the annealing zone is 400℃, the annealing time is 9h; seed crystal is added during the crystal growth process, and finally a CuInTe2-based thermoelectric semiconductor crystal with a diameter of 30mm and a length of 100mm is obtained.

[0028] Example 5 A preparation method of a CuInTe2-based thermoelectric semiconductor crystal, comprising the following steps: S1: melt the raw material elements Cu, In and Te in a molar ratio of 1:0.9:2.2, vacuum seal them in a quartz crucible with a conical bottom and a taper of 30°, and vacuumize to a degree of 10 -3 Pa, melt them in a rocking furnace, the rocking speed of the rocking furnace is 30r / min, the rocking time is 2h, the melting temperature is 1050℃, the heating speed is 2℃ / min, and after melting, cool to obtain CuInTe2-based polycrystal; S2: melt-growth the CuInTe2-based polycrystal from top to bottom in a vertical growth furnace, which is carried out in sections, in order: the temperature of the melting zone is 1050℃, the residence time is 15h; the temperature of the crystal growth zone is 900℃, the temperature decreasing speed from top to bottom is 10℃ / cm, the crystal growth speed is 1mm / h; the temperature of the annealing zone is 500℃, the annealing time is 10h; seed crystal is added during the crystal growth process, and finally a CuInTe2-based thermoelectric semiconductor crystal with a diameter of 30mm and a length of 100mm is obtained.

[0029] Example 6 A preparation method of a CuInTe2-based thermoelectric semiconductor crystal, comprising the following steps: S1: melt the raw material elements Cu, In and Te in a molar ratio of 1:1.1:2, vacuum seal them in a quartz crucible with a conical bottom and a taper of 30°, and vacuumize to 10 -3 Pa, melt them in a rocking furnace, the rocking speed of the rocking furnace is 20r / min, the rocking time is 1.5h, the melting temperature is 1050℃, the heating speed is 2℃ / min, and after melting, cool to obtain CuInTe2-based polycrystal; S2: melt-growth the CuInTe2-based polycrystal from top to bottom in a vertical growth furnace, which is carried out in sections, in order: the temperature of the melting zone is 1050℃, the residence time is 14h; the temperature of the crystal growth zone is 800℃, the temperature decreasing speed from top to bottom is 5℃ / cm, the crystal growth speed is 1.5mm / h; the temperature of the annealing zone is 400℃, the annealing time is 9h; seed crystal is not added during the crystal growth process, and finally a CuInTe2-based thermoelectric semiconductor crystal with a diameter of 30mm and a length of 100mm is obtained.

[0030] Example 7 A preparation method of a CuInTe2-based thermoelectric semiconductor crystal, comprising the following steps: S1: melt the raw material elements Cu, In and Te in a molar ratio of 1:1.2:2.2, vacuum seal them in a quartz crucible with a conical bottom and a taper of 30°, and vacuumize to 10 -3 Pa, melt them in a rocking furnace, the rocking speed of the rocking furnace is 20r / min, the rocking time is 3h, the melting temperature is 1100℃, the heating speed is 2℃ / min, and after melting, cool to obtain CuInTe2-based polycrystal; S2: CuInTe2-based polycrystalline material is melt-grown from top to bottom in a vertical growth furnace, divided into sections. The melting zone temperature is 1100℃, and the residence time is 18h. The crystal growth zone temperature is 900℃, with a temperature decrease rate of 10℃ / cm from top to bottom, and the crystal growth rate is 2mm / h. The annealing zone temperature is 500℃, and the annealing time is 10h. No seed crystal is added during the crystal growth process, and a CuInTe2-based thermoelectric semiconductor crystal with a diameter of 30mm and a length of 100mm is finally obtained.

[0031] Example 8 A method for preparing a CuInTe2-based thermoelectric semiconductor crystal includes the following steps: S1: Mix and melt the raw materials elemental Cu, elemental In, and elemental Te in a molar ratio of 1:0.9:2, and place the mixture into a quartz crucible with a conical bottom and a taper of 30°. Seal the crucible under vacuum at a vacuum level of 10. -3 Pa was placed in a swaying furnace for melting. The swaying rate of the furnace was 20 r / min, the swaying time was 2 h, the melting temperature was 1050 ℃, and the heating rate was 2 ℃ / min. After melting and cooling, CuInTe2-based polycrystalline material was obtained. S2: CuInTe2-based polycrystalline material is melt-grown from top to bottom in a vertical growth furnace, divided into sections: the melting zone temperature is 1050℃, and the residence time is 14h; the crystal growth zone temperature is 650℃, with a temperature decrease rate of 5℃ / cm from top to bottom, and the crystal growth rate is 1.5mm / h; the annealing zone temperature is 400℃, and the annealing time is 9h; no seed crystal is added during the crystal growth process, and finally a CuInTe2-based thermoelectric semiconductor crystal with a diameter of 30mm and a length of 100mm is obtained.

[0032] Example 9 A method for preparing a CuInTe2-based thermoelectric semiconductor crystal includes the following steps: S1: Mix and melt the raw materials elemental Cu, elemental In, and elemental Te in a molar ratio of 1:1:2, and place the mixture into a quartz crucible with a conical bottom and a taper of 30°. Seal the crucible under vacuum at a vacuum level of 10. -3 Pa was placed in a swaying furnace for melting. The swaying rate of the furnace was 20 r / min, the swaying time was 2 h, the melting temperature was 1050 ℃, and the heating rate was 2 ℃ / min. After melting and cooling, CuInTe2-based polycrystalline material was obtained. S2: CuInTe2-based polycrystal is subjected to melt growth from top to bottom in a vertical growth furnace, and is subjected to zoning, in sequence, melt zone temperature is 1050℃, residence time is 12h; crystal growth zone temperature is 650℃, temperature decreasing speed from top to bottom is 5℃ / cm, crystal growth speed is 1mm / h; annealing zone temperature is 400℃, annealing time is 9h; no seed crystal is added in the process of crystal growth, finally CuInTe2-based thermoelectric semiconductor crystal with diameter of 30mm and length of 100mm is obtained.

[0033] Comparative Example 1 A preparation method of CuInTe2-based thermoelectric semiconductor crystal, comprising the following steps: S1: raw material single element Cu, single element In and single element Te are mixed and melted according to molar ratio of 1:0.5:2.1, are vacuum sealed in quartz crucible with conical bottom and taper of 30°, vacuum degree is 10 -3 Pa, the melt is loaded into a rocking furnace, the rocking speed of the rocking furnace is 20r / min, the rocking time is 1h, the melting temperature is 1000℃, the heating speed is 4℃ / min, after melting, CuInTe2-based polycrystal is obtained by cooling; S2: CuInTe2-based polycrystal is subjected to melt growth from top to bottom in a vertical growth furnace, and is subjected to zoning, in sequence, melt zone temperature is 1050℃, residence time is 12h; crystal growth zone temperature is 650℃, temperature decreasing speed from top to bottom is 5℃ / cm, crystal growth speed is 1mm / h; annealing zone temperature is 400℃, annealing time is 9h; no seed crystal is added in the process of crystal growth, finally CuInTe2-based thermoelectric semiconductor crystal with diameter of 30mm and length of 100mm is obtained.

[0034] Comparative Example 2 A preparation method of CuInTe2-based thermoelectric semiconductor crystal, comprising the following steps: S1: raw material single element Cu, single element In and single element Te are mixed and melted according to molar ratio of 1:0.8:2.5, are vacuum sealed in quartz crucible with conical bottom and taper of 30°, vacuum degree is 10 -3 Pa, the melt is loaded into a rocking furnace, the rocking speed of the rocking furnace is 20r / min, the rocking time is 1h, the melting temperature is 1000℃, the heating speed is 4℃ / min, after melting, CuInTe2-based polycrystal is obtained by cooling; S2: CuInTe2-based polycrystal is subjected to melt growth from top to bottom in a vertical growth furnace, and is subjected to zoning, in sequence, melt zone temperature is 1000℃, residence time is 12h; crystal growth zone temperature is 800℃, temperature decreasing speed from top to bottom is 5℃ / cm, crystal growth speed is 2mm / h; annealing zone temperature is 400℃, annealing time is 9h; no seed crystal is added in the process of crystal growth, finally CuInTe2-based thermoelectric semiconductor crystal with diameter of 30mm and length of 100mm is obtained.

[0035] Comparative Example 3 A preparation method of CuInTe2-based thermoelectric semiconductor crystal, comprising the following steps: S1: raw material elements Cu, In, Sb and Te are mixed and melted according to molar ratio of 1:0.8:0.2:2.1, are vacuum sealed in a quartz crucible with conical bottom and taper of 30°, and vacuum degree is 10 -3 Pa, the quartz crucible is loaded into a rocking furnace to be melted, rocking speed of the rocking furnace is 20r / min, rocking time is 2h, melting temperature is 1000℃, and heating speed is 4℃ / min, after melting, the quartz crucible is cooled to obtain CuInTe2-based polycrystal; S2: CuInTe2-based polycrystal is subjected to melt growth from top to bottom in a vertical growth furnace, and is subjected to zoning, in sequence, melt zone temperature is 1000℃, residence time is 12h; crystal growth zone temperature is 800℃, temperature decreasing speed from top to bottom is 5℃ / cm, crystal growth speed is 2mm / h; annealing zone temperature is 400℃, annealing time is 9h; no seed crystal is added in the process of crystal growth, finally CuInTe2-based thermoelectric semiconductor crystal with diameter of 30mm and length of 100mm is obtained.

[0036] Comparative Example 4 In this comparative example, CuInTe2-based thermoelectric semiconductor crystal is prepared by spark plasma sintering method disclosed in Chem. Commun, 2012, 48, 3818-3820, comprising the following steps: Raw material elements Cu, In and Te are sealed in a vacuum silica gel tube according to molar ratio of 1:1:2, heated to 900℃, heated for 10h, kept at this temperature for 12h, then cooled to 650℃ at a speed of 5℃ / min, after annealing at 650℃, the ingot is crushed into fine powder, then spark plasma sintering is carried out at 600℃ for 5-10min in argon, finally dense CuInTe2-based thermoelectric semiconductor crystal is obtained.

[0037] Test Example Test results of Examples 1-9 and Comparative Examples 1-4 are shown in Table 1 below, According to the test results of Examples 1-9 and Comparative Examples 1-4, the CuInTe2-based thermoelectric semiconductor crystal of the present application has a thermal conductivity of 0.7-6.7 Wm -1 K -1 , preferably 0.7-5.5 Wm -1 K -1 ; a power factor of 4.6-14.8 μWcm -1 K -2 , preferably 6.8-14.8 μWcm -1 K -2 ; a Seebeck coefficient of 275-390 μVK -1 ; and an electrical conductivity of 0.02*10 5 -0.17*10 5 S m -1 .

[0038] The present application improves the thermoelectric performance of the CuInTe2-based thermoelectric semiconductor crystal by regulating intrinsic defects, improving carrier concentration and migration rate, changing lattice structure, enhancing phonon scattering, improving power factor and Seebeck coefficient, and reducing thermal conductivity. Examples 1-4, under the condition of In-poor and Te-rich, induce vacancies, increase carrier concentration, and form double phonon scattering centers with interstitial Te, effectively reducing the thermal conductivity of high lattice. By controlling the intrinsic defects through proportioning, and by controlling the melting temperature and residence time during crystal growth, the present application avoids excessive volatilization loss of raw materials, controls the formation of point defects, and ensures the uniformity of distribution. The In-rich and Te-rich condition in Example 7 can cause uniform distortion of the lattice without affecting the migration of carriers, reducing the thermal conductivity and improving the power factor. Examples 5 and 6 are Te-rich and In-rich, respectively. When the amount of Te is slightly more, interstitial atoms can be formed, increasing the phonon scattering channel. When the amount of In is slightly more, anti-site defects are formed between Cu and In, changing the lattice size. Example 8, under the condition of In-poor, forms hole carriers, causing changes in lattice structure and enhancing phonon scattering. The selective addition of seed crystals during crystal formation in Examples 3 and 5 can guide the formation of crystals and control the crystal growth zone temperature and temperature decrement rate, further preventing the random growth orientation of crystals. The absence of seed crystals during crystal formation can further promote the uniform distribution of intrinsic defects.

[0039] The test results show that the thermal conductivity increases and the power factor decreases. When the amount of In is too small, the crystal lattice structure is difficult to form, the stability is reduced, and the carrier mobility is reduced; when the amount of Te is too much, the diffusion effect is poor, and the agglomeration occurs, which affects the phonon scattering and the carrier mobility, resulting in poor improvement effect of the thermoelectric performance of the CuInTe2-based thermoelectric semiconductor crystal. The test results show that the two methods have no obvious improvement effect on the thermoelectric performance of the CuInTe2-based thermoelectric semiconductor crystal, wherein the introduction of impurities by doping other elements causes defects and disorder, which weakens the effect of reducing the thermal conductivity; the discharge plasma sintering method is not optimized in the partition temperature, which easily leads to uneven distribution of raw materials in the melt during the melting process of the raw materials, affects the carrier mobility, and is difficult to control the nucleation and defect density in the crystal growth process. Controlling the crystal growth rate plays an important role in improving the stability of the solidification interface, and controlling the annealing conditions can promote the growth of the crystal size and the formation of point defects. Therefore, the lack of condition control leads to the fact that the crystal power factor and the Seebeck coefficient are obviously lower at room temperature.

Claims

1. A CuInTe2-based thermoelectric semiconductor crystal, characterized in that, Raw materials include: elemental Cu, elemental In, and elemental Te; The molar ratio of elemental Cu, elemental In, and elemental Te is 1: (0.8-1.2): (2-2.2).

2. The CuInTe2-based thermoelectric semiconductor crystal according to claim 1, characterized in that, The power factor of the CuInTe2-based thermoelectric semiconductor crystal is 6.8-14.8 μWcm at 300-800 K. -1 K -2 .

3. A CuInTe2-based thermoelectric semiconductor crystal according to claim 1 or 2, characterized in that, The Seebeck coefficient of the CuInTe2-based thermoelectric semiconductor crystal is 275-390 μVK at 300-800 K. -1 .

4. A CuInTe2-based thermoelectric semiconductor crystal according to claim 1 or 2, characterized in that, The CuInTe2-based thermoelectric semiconductor crystal has a thermal conductivity of 0.7-5.5 W / m² at 300-800 K. -1 K -1 .

5. A CuInTe2-based thermoelectric semiconductor crystal according to claim 1 or 2, characterized in that, The CuInTe2-based thermoelectric semiconductor crystal has an electrical conductivity of 0.02 × 10⁻⁶ K at 300-800 K. 5 -0.17×10 5 S m -1 .

6. A CuInTe2-based thermoelectric semiconductor crystal according to claim 1 or 2, characterized in that, The CuInTe2-based thermoelectric semiconductor crystal has a diameter of 10-40 mm and a length of 10-100 mm.

7. A CuInTe2-based thermoelectric semiconductor crystal according to claim 6, characterized in that, The diameter of the CuInTe2-based thermoelectric semiconductor crystal is 15-40 mm.

8. A method for preparing a CuInTe2-based thermoelectric semiconductor crystal according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Mix and melt elemental Cu, elemental In, and elemental Te, and then cool to obtain CuInTe2-based polycrystalline material; S2: CuInTe2-based polycrystalline material is melt-grown from top to bottom, with or without seed crystals added during the crystal growth process, to obtain CuInTe2-based thermoelectric semiconductor crystal.

9. The method for preparing a CuInTe2-based thermoelectric semiconductor crystal according to claim 8, characterized in that, In step S1, elemental Cu, elemental In, and elemental Te are mixed and placed into a quartz crucible with a conical bottom and a taper of 18-44°, then vacuum-sealed at a vacuum level of 10. -2 -10 -3 Pa is loaded into a vertical melting furnace or a swaying furnace and melted at a temperature of 1000-1100℃ and a heating rate of 2-10℃ / min. After melting and cooling, CuInTe2-based polycrystalline materials are obtained. The swing rate of the swing furnace is 10-30 r / min, and the swing time is 0.5-3 h.

10. The method for preparing a CuInTe2-based thermoelectric semiconductor crystal according to claim 8, characterized in that, In step S2, melt growth is carried out in sections within a vertical growth furnace: the temperature of the melting zone is 1000-1100℃, and the residence time is 8-18h; the temperature of the crystal growth zone is 650-950℃, the temperature decrease rate from top to bottom is 5-15℃ / cm, and the crystal growth rate is 0.5-2mm / h; the temperature of the annealing zone is 300-500℃, and the annealing time is 8-10h.

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