Full-temperature-section stable beta cubic phase Cu-Se-based thermoelectric material and preparation method thereof

Abstract

The invention discloses a full-temperature-range stable beta cubic phase Cu-Se-based thermoelectric material and a preparation method thereof, and belongs to the field of thermoelectric materials. The chemical formula of the Cu < 1.8-x > Bi < x > Se < 1-2y > SyTe < y >, wherein 0.01 lt; xlt; 0.1, 0.025 lt, 0.025 lt; yt; Yt; and 0.1. The stable beta phase is kept between 300K and 773K, and the maximum thermoelectric figure of merit coefficient ZT which is equal to 1.33 can be obtained at the temperature of 500 DEG C. According to the material, the carrier concentration is effectively adjusted by alloying the Bi element at the Cu position; s and Te elements are alloyed at the Se position, so that the lattice heat conductivity is effectively reduced, and the thermoelectric performance is greatly optimized while the beta phase is kept. The problems that phase change of a Cu-Se-based thermoelectric material is not beneficial to the stability of a device, the service life is short and the like are effectively solved, in addition, the related elements are rich in storage and low in price, the preparation process is simple, and large-scale production and commercial application are facilitated.

Description

Technical Field

[0001] The present invention belongs to the field of thermoelectric materials, and particularly relates to a thermoelectric material with a stable cubic β-phase in the whole temperature range of copper, bismuth, sulfur, selenium, and tellurium and a preparation method thereof. Technical Background

[0002] In recent years, liquid Cu 2-x Se-based thermoelectric materials have received extensive attention due to their excellent thermoelectric properties and non-toxic components. However, as the temperature gradually decreases to room temperature, Cu 2-x Se will transform from the β-phase to the α-phase, and this transformation occurs at about 400 K. The β-phase usually has a cubic structure similar to zinc blende, while the α-phase includes monoclinic, triclinic, tetragonal, orthorhombic, or a mixture of several other phases. Considering that the phase change may exacerbate the unreliability of the device, obtaining the β-phase at room temperature can effectively enhance the stability of the device.

[0003] Research shows that a stable cubic phase can be achieved near room temperature by introducing an appropriate amount of Cu vacancies. However, too many Cu vacancies will lead to a high carrier concentration, deviating from the optimal carrier concentration range for achieving a high ZT value. For example, in cubic Cu 2-x Se(0.15≤x≤0.2) materials at room temperature, the ZT value of the Cu 1.86 Se sample (x = 0.14) is 0.2 at 723 K. In contrast, the ZT value of the Cu 1.85 Se sample (x = 0.15) is lower than 0.15 at the same temperature. It can be seen that the cubic structure, stability, and thermoelectric properties at room temperature are related to the content of Cu vacancies. Therefore, decoupling these factors to achieve excellent stability and high thermoelectric performance has become the core concern in the current research on Cu 2-x Se-based thermoelectric materials. Summary of the Invention

[0004] Aiming at the problem of the unstable β-phase of Cu 2-x Se at room temperature in the prior art, the present invention provides a high-performance Cu-Se-based thermoelectric material with a stable cubic β-phase in the whole temperature range and a preparation method thereof.

[0005] The technical solution of the present invention is a high-performance and stable cubic-phase Cu-Se-based thermoelectric material with the chemical formula Cu 1.8-x Bi x Se 1-2y S y Te y , 0.01 < x < 0.1; 0.025 < y < 0.1, which is a cubic-phase structure between 300 K and 773 K, and the highest ZT value is 1.33;

[0006] A high-performance and stable cubic-phase copper selenide-based thermoelectric material with the chemical formula Cu1.8-x Bi x Se 1- 2y S y Te y , where 0.01 <x<0.1,0.025<y<0.1;

[0007] The technical solution of the cubic phase Cu-Se based thermoelectric material of the present invention is:

[0008] The Cu 1.8 In the first step, the electronic structure of the material was changed by introducing Bi into the Cu site, thereby optimizing the Cu 1.8 Se carrier concentration and significantly improved its thermoelectric performance. 1.7 Bi 0.1 Se, we further doped S and Te elements at the Se site, introduced more elements and caused local atomic disorder inside the lattice. This disordered state has almost no scattering effect on small-scale carriers, but exhibits a strong scattering effect on large-scale phonon transport. Therefore, it can effectively reduce thermal conductivity while maintaining electrical properties, ultimately optimizing thermoelectric performance.

[0009] The technical solution of the present invention is a full-temperature stable β-phase Cu-Se basic thermoelectric material, the chemical formula of which is Cu 1.8- x Bi x Se 1-2y S y Te y , where 0.01 <x<0.1,0.025<y<0.1。

[0010] Further, x=0.01, 0.03, 0.05, 0.07, 0.09 or 0.1.

[0011] Further, y=0.025, 0.05, 0.075 or 0.1.

[0012] Further, x = 0.1, y = 0.1;

[0013] A method for preparing a full-temperature stable β-phase Cu-Se basic thermoelectric material specifically comprises the following steps:

[0014] Step 1: Loading;

[0015] According to Cu 1.8-x Bi x Se 1-2y S y Te yThe stoichiometric ratio, where 0.1 < x < 0.1; 0.025 < y < 0.1; Weigh the Cu, Bi, S, Se and Te elemental substances separately in an Ar atmosphere;

[0016] Step 2: Ball milling;

[0017] In an Ar atmosphere, ball mill all the elemental substances weighed in Step 1 to alloy them, obtaining Cu 1.8-x Bi x Se 1- 2y S y Te y nanopowder, where the ball milling time is 10 - 15 h;

[0018] Step 3: Sintering;

[0019] Transfer the powder obtained in Step 2 to a graphite mold, and place the graphite punch column into the mold. Keep it at 300 - 500 °C under a pressure of 8750 - 10000 N for 5 minutes to fully sinter the sample to form a dense structure;

[0020] Furthermore, in Step 1, the ball milling tank is a 304 stainless steel ball milling tank, and two ball milling beads are used, which are 304 stainless steel beads with diameters of 12.72 and 6.35 cm respectively.

[0021] Furthermore, in Step 2, the ball milling time is 10 h.

[0022] Furthermore, in Step 3, the heating rate is 100 °C / min, and it needs to be slowly cooled after sintering.

[0023] Furthermore, in Step 3, the pressure of the graphite punch column is 9375 N.

[0024] The beneficial effects of the present invention are as follows:

[0025] A new type of stable and excellent - performance Cu - Se - based thermoelectric material is provided. This material maintains a stable β - phase between 300 K and 773 K, and the maximum thermoelectric figure of merit ZT is increased by more than ten times compared with the original Cu1.8Se, making it possible to prepare high - performance and stable thermoelectric devices for Cu - Se thermoelectric materials. Description of the Drawings

[0026] Figure 1 For the XRD diffraction patterns of Cu 1.8-x Bi x Se, where x = 0.01, 0.03, 0.05, 0.07, 0.09 or 0.1 series of samples in Example 2, indicating that Cu 1.8-x Bi x Se maintains a β - cubic phase at room temperature.

[0027] Figure 2 Cu in Example 3 1.7 Bi 0.1 Se 1-2y S y Te y , where y = 0.025, 0.05, 0.075 or 0.1, the XRD diffraction patterns of the samples show that Cu 1.7 Bi 0.1 Se 1-2y S y Te y The β-cubic phase is maintained at room temperature.

[0028] Figure 3 Cu in Example 2 1.7 Bi 0.1 The temperature-dependent XRD diffraction patterns of Se samples show that Cu 1.7 Bi 0.1 Se remains in the cubic phase between 300K and 773K.

[0029] Figure 4 Cu in Example 3 1.7 Bi 0.1 Se 0.8 S 0.1 Te 0.1 The temperature-dependent XRD diffraction patterns of the samples show that Cu 1.7 Bi 0.1 Se 0.8 S 0.1 Te 0.1 The cubic phase is maintained between 300K and 773K.

[0030] Figure 5 Cu in Example 2 1.8-x Bi x Se, where x = 0.01, 0.03, 0.05, 0.07, 0.09 or 0.1, is a graph showing the variation of the thermoelectric figure of merit ZT of a series of samples with temperature.

[0031] Figure 6 Cu in Example 3 1.7 Bi 0.1 Se 1-2y S y Te y , where y = 0.025, 0.05, 0.075 or 0.1, is a graph showing the variation of the thermoelectric figure of merit ZT of a series of samples with temperature. DETAILED DESCRIPTION

[0032] A method for preparing a full-temperature stable β-phase Cu-Se basic thermoelectric material specifically comprises the following steps:

[0033] Step 1: Loading

[0034] According to the stoichiometric ratio of Cu 1.8-x Bi x Se 1-2y S y Te y (0.01 < x < 0.1, 0.025 < y < 0.1), in a glove box under an Ar atmosphere, weigh the elemental substances of Cu, Bi, S, Se, and Te respectively and place them in a ball milling jar. Then, put a large ball and a small ball in the ball milling jar and seal them together, where 0.01 < x < 0.1, 0.025 < y < 0.1;

[0035] Step 2: Ball milling

[0036] Put the ball milling jar described in Step 1 into a high-energy ball mill in an Ar atmosphere and ball mill it to alloy it, obtaining Cu 1.8- x Bi x Se 1-2y S y Te y nano powder, where the ball milling time is 10 - 15 h; the ball milling jar is a 304 stainless steel ball milling jar, and the ball milling beads are 304 stainless steel beads with diameters of 12.72 and 6.35 cm respectively

[0037] Step 3: Sintering;

[0038] Transfer the powder obtained in Step 2 to a graphite mold, and put a graphite punch column into the mold. Keep it at 300 - 500 °C under a pressure of 8750 N for 5 minutes to fully sinter the sample to form a dense structure, where the hole diameter of the graphite mold used is 13 mm and the sample loading of the mold is 2 g.

[0039] Furthermore, the ball milling time in Step 2 is 10 h.

[0040] Furthermore, the heating rate in Step 3 is 100 °C / min, and it needs to be slowly cooled after sintering.

[0041] Example 1:

[0042] Step 1: Loading

[0043] In a glove box under an Ar atmosphere, according to the stoichiometric ratio of Cu 1.8 Se, weigh the elemental substances of Cu and Se respectively and place them in a ball milling jar. Then, add a large ball and a small ball to the ball milling jar and seal them together.

[0044] Step 2: Ball milling

[0045] Place the ball milling jar described in Step 1 in a high-energy ball mill and ball mill it at a speed of 800 r / min for 10 hours.

[0046] Step 3: Sintering

[0047] The sample obtained in step 2 was placed in a graphite mold in a glove box protected by Ar atmosphere, and the mold was sintered in a hot press at a sintering temperature of 300°C, a heating rate of 100°C / min, a holding pressure of 9375N, and a holding time of 5min to obtain Cu 1.8 Se bulk thermoelectric material.

[0048] Example 2:

[0049] Step 1: Loading

[0050] In an Ar atmosphere glove box, the Cu 1.8-x Bi x Se (x = 0.01, 0.03, 0.05, 0.07, 0.09 and 0.1), Cu, Bi and Se were weighed respectively and placed in a ball mill, and then a large bead and a small bead were added to the ball mill and sealed together.

[0051] Step 2: Ball Milling

[0052] The ball mill described in step 1 is placed in a high-energy ball mill and ball milled at a rotation speed of 800 r / min for 10 hours.

[0053] Step 3: Sintering

[0054] The sample obtained in step 2 was placed in a graphite mold in a glove box protected by Ar atmosphere, and the mold was sintered in a hot press at a sintering temperature of 300°C, a heating rate of 100°C / min, a holding pressure of 9375N, and a holding time of 5min to obtain Cu 1.8-x Bi x Se (x = 0.01, 0.03, 0.05, 0.07, 0.09 and 0.1) bulk thermoelectric materials.

[0055] Example 3:

[0056] Step 1: Loading

[0057] In an Ar atmosphere glove box, the Cu 1.7 Bi 0.1 Se 1-2y S y Te y The stoichiometric ratios of Cu, Bi, Se, S and Te were respectively weighed and placed in a ball mill, and then a large bead and a small bead were added to the ball mill and sealed together.

[0058] Step 2: Ball Milling

[0059] The ball mill described in step 1 is placed in a high-energy ball mill and ball milled at a speed of 800 r / min for 10 hours.

[0060] Step 3: Sintering

[0061] The sample obtained in step 2 was placed in a graphite mold in a glove box protected by Ar atmosphere, and the mold was sintered in a hot press at a sintering temperature of 300°C, a heating rate of 100°C / min, a holding pressure of 10000N, and a holding time of 5min to obtain Cu 1.7 Bi 0.1 Se 1-2y S y Te y (y=0.025, 0.05, 0.075 and 0.1) bulk thermoelectric material.

Claims

1. A full-temperature stable β-cubic phase Cu-Se based thermoelectric material, the chemical formula of which is Cu 1.8-x Bi x Se 1- 2y S y Te y , where 0.01 <x<0.1,0.025<y<0.1。 2. The full-temperature stable β-cubic phase Cu-Se based thermoelectric material according to claim 1, characterized in that: x=0.01, 0.03, 0.05, 0.07, 0.09 or 0.

1.

3. The full-temperature stable β-cubic phase Cu-Se based thermoelectric material according to claim 1, characterized in that: y=0.025, 0.05, 0.075 or 0.

1.

4. The full-temperature stable β-cubic phase Cu-Se based thermoelectric material according to claim 1, characterized in that: x=0.1, y=0.

1.

5. A method for preparing a full-temperature stable β-cubic phase Cu-Se based thermoelectric material, comprising the following steps: Step 1: Loading; According to the stoichiometric ratio of Cu 1.8-x Bi x Se 1-2y S y Te y where 0.1 < x < 0.1; 0.025 < y < 0.1; Weigh the elemental substances of Cu, Bi, S, Se and Te respectively in an Ar atmosphere; Step 2: ball milling; All the elements weighed in step 1 were ball-milled in an Ar atmosphere to alloy them and obtain Cu 1.8-x Bi x Se 1-2y S y Te y Nano powder; Step 3: sintering; The powder obtained in step 2 is transferred to a graphite mold, and a graphite punch is placed in the mold and maintained at 300-500° C. for 5 minutes under a pressure of 8750-10000 N to allow the sample to be fully sintered to form a dense structure.

6. The method for preparing a full-temperature stable β-cubic phase Cu-Se based thermoelectric material according to claim 5, characterized in that: The ball mill in step 1 is a 304 stainless steel ball mill, and two ball mill beads are used, the diameters of which are 12.72 and 6.35 cm, respectively.

7. The method for preparing a full-temperature stable β-cubic phase Cu-Se based thermoelectric material according to claim 5, characterized in that: The ball milling time in step 2 is 10 h.

8. The method for preparing a full-temperature stable β-cubic phase Cu-Se based thermoelectric material according to claim 5, characterized in that: The heating rate in step 3 is 100°C / min, and slow cooling is required after sintering is completed.

9. The method for preparing a full-temperature stable β-cubic phase Cu-Se based thermoelectric material according to claim 5, characterized in that: The graphite punch pressure in step 3 is 9375N.

Images