Beta-srzrs3 thermoelectric conversion bulk material and method for producing the same

Abstract

The application belongs to the technical field of thermoelectric materials, and provides a preparation method of a beta-SrZrS3 thermoelectric conversion bulk material, which comprises the following steps: subjecting SrZrO3 powder to a sulfuration reaction to obtain beta-SrZrS3 powder; and subjecting the beta-SrZrS3 powder to rapid hot-press sintering to obtain the beta-SrZrS3 thermoelectric conversion bulk material. The preparation method has the advantages of low cost, simplicity and rapidness, can realize batch synthesis of SrZrS3 bulk materials, shorten the synthesis period, and obtain the beta-SrZrS3 thermoelectric conversion bulk material with pure phase, uniform composition distribution and high density. The raw material used is SrZrO3 powder which is inexpensive, non-toxic and does not require inert storage environment. The vacuum tube furnace and the rapid hot-press furnace are used, the sulfuration reaction and the hot-press sintering are used for preparation, and since the raw material, the preparation process and the target product meet the requirements of environmental friendliness, the preparation method can be directly extended to the development of the application of perovskite sulfide thermoelectric conversion, and provides a new way for the development of a new thermoelectric system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermoelectric materials, and particularly relates to a beta-SrZrS3 thermoelectric conversion bulk material and a preparation method thereof. BACKGROUND

[0002] Thermoelectric materials are energy materials that can directly realize the mutual conversion of temperature difference and electric energy, and have important applications in space exploration, precision refrigeration, wearable device power supply and the like. The sulfide perovskite system has the advantages of low toxicity, high reserves, stable structure and adjustable band gap, and its thin film material has been applied to photoelectric detection and solar cells, but the research on thermoelectric conversion applications is less. Among them, BaZrS3 has a distorted perovskite structure and a band gap of ~1.8 eV, and experiments have confirmed its potential for good thermoelectric performance, but its preparation temperature is high (~1500℃), and the bulk material is easy to crack, which makes it difficult to form, limiting the further development of its thermoelectric conversion applications. Therefore, it is necessary to develop sulfide perovskite thermoelectric materials with low price, simple and convenient preparation method and good forming performance.

[0003] SrZrS3 is a new type of perovskite material, and the content of its constituent elements Sr, Zr and S in the earth's crust is 370, 165 and 350 ppm, respectively, which is much higher than the commonly used components of Ge, Cd, In, Se, Te (1.4, 0.15, 0.25, 0.05, 0.001 ppm) and other thermoelectric and photoelectric materials, and is environmentally friendly. Unlike BaZrS3, the bonding characteristics of SrZrS3 make it have unique mechanical properties and are easier to form, which is conducive to the preparation of large-size bulk materials or target materials, and at the same time, its wider band gap of ~2.3 eV can inhibit the bipolar effect that causes the performance of thermoelectric materials to decrease at high temperatures; in addition, SrZrS3 has two crystal structures, alpha-SrZrS3 and beta-SrZrS3, which exhibit different energy band structures and transport properties, providing more space for physical property regulation. The above factors all indicate the potential of SrZrS3 material for thermoelectric applications.

[0004] However, the main method for preparing SrZrS3 bulk material at present is high-temperature melting of Sr, Zr, S elements or SrS, Zr, S or SrS, ZrS2 for tens of hours or days, which has problems such as easy oxidation, high cost, large difference in melting point, easy volatilization of raw materials, and long preparation period and energy consumption; in addition, SrZrS3 has two crystal structures, α-SrZrS3 is a needle-shaped phase, connected by ZrS6 octahedron sharing edges, that is, NH4CdCl3 structure; and β-SrZrS3 is a distorted perovskite structure, connected by ZrS6 octahedron sharing vertices, that is, GdFeO3 structure, so the preparation of SrZrS3 needs to consider the competition of the two phases. The existing technology (Journal of Physical Review Materials, 2023, 7, 085403.) discloses the bonding characteristics and energy band structure of β-SrZrS3, and indicates the possibility of high thermoelectric performance, but the existing technology (Journal of Nano Letters, 2015, 15, 581-585.) discloses that the α-SrZrS3 phase is more stable under standard conditions, and the experimental conditions need to be controlled to prepare the β-SrZrS3 phase, and there is no experimental study on the thermoelectric performance of the β-SrZrS3 bulk material at present. Therefore, it is urgent to develop a new type of low-cost, simple, convenient and efficient preparation technology to obtain a pure phase and high-density β-SrZrS3 bulk material, which has important significance for the research and development of thermoelectric materials. SUMMARY

[0005] The purpose of the embodiment of the present application is to provide a preparation method of β-SrZrS3 thermoelectric conversion bulk material, aiming at solving the problems raised in the above background.

[0006] The embodiment of the present application is implemented in this way, a preparation method of β-SrZrS3 thermoelectric conversion bulk material, comprising the following steps:

[0007] (1) sulfidizing SrZrO3 powder to obtain β-SrZrS3 powder;

[0008] (2) rapidly hot-pressing and sintering the β-SrZrS3 powder into a block to obtain the β-SrZrS3 thermoelectric conversion bulk material.

[0009] Preferably, the step of sulfidizing SrZrO3 powder to obtain β-SrZrS3 powder is specifically:

[0010] (1) placing SrZrO3 powder in a tube furnace and vacuumizing;

[0011] (2) introducing CS2 gas into the furnace;

[0012] (3) heating the tube furnace and keeping temperature, and obtaining the β-SrZrS3 powder after cooling to room temperature.

[0013] Preferably, in step (2), the flow rate of the CS2 gas is 35-60 SCCM.

[0014] Preferably, in step (3), the tube furnace is heated to 1000-1200℃, the internal gas pressure is 35-80 Pa, and the temperature is kept for 1-12 h.

[0015] Preferably, the step of rapidly hot-pressing and sintering the β-SrZrS3 powder into a block to obtain the β-SrZrS3 thermoelectric conversion block material comprises:

[0016] (1) pre-pressing the β-SrZrS3 powder in a mold, and then placing it in a rapid hot-pressing and sintering furnace and vacuumizing;

[0017] (2) controlling the temperature in the furnace to reach 1300℃, keeping the temperature for 5 min, and the pressure is 50 MPa, and obtaining the β-SrZrS3 thermoelectric conversion block material after cooling to room temperature.

[0018] Preferably, in step (1), the mold is a graphite mold.

[0019] Another object of the embodiment of the present application is to provide a β-SrZrS3 thermoelectric conversion block material prepared by the above preparation method.

[0020] The preparation method of the β-SrZrS3 thermoelectric conversion block material provided by the embodiment of the present application has the advantages of low cost, simplicity and rapidness, can realize batch synthesis of the β-SrZrS3 block material and shorten the synthesis period, the raw material used is inexpensive and non-toxic SrZrO3 powder, and there is no need for inert storage environment, a vacuum tube furnace and a rapid hot-pressing furnace are used, the preparation is performed through sulfidation reaction and hot-pressing sintering, and since the raw material, the preparation process and the target product are basically environmentally friendly, the preparation method provided by the embodiment of the present application can be directly extended to the development of the application of the perovskite sulfide thermoelectric conversion, and provides a new way for the development of a new thermoelectric system.

[0021] The β-SrZrS3 thermoelectric conversion block material prepared has pure phase, uniform composition distribution and high density (up to 100%), according to performance testing, the Seebeck coefficient is up to -475.5 μVK −1 at 323 K, the thermal conductivity is 2.2 Wm −1 K −1 , has significant thermoelectric effect and low thermal conductivity, and indicates that it is a potential medium-temperature thermoelectric material. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A flowchart illustrating a method for preparing a β-SrZrS3 thermoelectric conversion bulk material according to an embodiment of the present invention;

[0023] Figure 2 The XRD pattern of the sample provided in Embodiment 1 of the present invention;

[0024] Figure 3 The above are SEM morphology images of the sample provided in Embodiment 1 of the present invention, where (a) and (b) are morphology display results at different magnifications;

[0025] Figure 4 The elemental distribution mapping diagram of the sample provided in Embodiment 1 of the present invention;

[0026] Figure 5 The EDS energy spectrum of the sample provided in Example 1 of this invention;

[0027] Figure 6 The variable-temperature thermoelectric performance results of the sample provided in Example 1 of the present invention are shown, where (a) is the Seebeck coefficient, (b) is the resistivity, (c) is the power factor, and (d) is the thermal conductivity. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] A β-SrZrS3 thermoelectric conversion bulk material, the preparation method of which is as follows: Figure 1 As shown, the specific steps include:

[0030] (1) Place SrZrO3 powder in a tube furnace and use a mechanical pump to evacuate the furnace body to <0.1 Pa;

[0031] (2) Introduce CS2 gas at a flow rate of 35-60 SCCM;

[0032] (3) Heat the tube furnace to 1000-1200 ℃, with an internal gas pressure of 35-80 Pa, keep it at that temperature for 1-12 h, and then cool it to room temperature to obtain β-SrZrS3 powder.

[0033] (4) Place the β-SrZrS3 powder in a graphite mold for pre-pressing, and then place it in a rapid hot pressing sintering furnace. Evacuate the furnace body to <0.1 Pa.

[0034] (5) Using infrared temperature measuring equipment to monitor the temperature of the sample cavity, so that it reaches 1300℃, and keeps for 5 min, the pressure is 50 MPa, and after cooling to room temperature, a β-SrZrS3 bulk sample is obtained.

[0035] The specific implementation of the present application is described in detail below in combination with specific examples.

[0036] Example 1, a β-SrZrS3 thermoelectric conversion bulk material, the preparation method comprising the following steps:

[0037] (1) Spread 325 mesh SrZrO3 powder on the bottom of the crucible, place the crucible in the middle of the tube furnace, use a mechanical pump to vacuum to <0.1 Pa, introduce CS2 gas from one end of the tube furnace, control the gas flow at 35 SCCM, adjust the valve to keep the gas pressure at 35 Pa, set the temperature rising curve to heat the furnace to 1000℃ and keep for 12 h, and naturally cool the furnace to room temperature, to obtain a red brown β-SrZrS3 powder precursor;

[0038] (2) After the β-SrZrS3 powder precursor is ground uniformly in a mortar, it is loaded into a graphite mold, the graphite mold is placed in a rapid sintering furnace, vacuum is applied, and then rapid hot-pressing sintering is carried out (pressure 50 MPa, temperature 1300℃, holding time 5 min) to obtain a β-SrZrS3 bulk material.

[0039] The β-SrZrS3 bulk material prepared in Example 1 is cut and processed as a sample for performance testing:

[0040] After measurement, the density of the sample is 3.9 gcm −3 , and the relative density is close to 100%;

[0041] The sample is analyzed by X-ray diffractometer, and the XRD pattern is as shown in Figure 2 , according to Figure 2 , it can be seen that it matches the standard spectrum PDF#04-007-5510 of SrZrS3;

[0042] The sample is analyzed by scanning electron microscope, and the SEM micrograph is as shown in Figure 3 , according to Figure 3 , it can be seen that the sample has high density;

[0043] The sample is analyzed by scanning transmission electron microscope, and the element distribution Mapping is as shown in Figure 4 , according to Figure 4 , it can be seen that the element distribution of the sample is uniform;

[0044] The sample is analyzed by energy dispersive spectrometer, and the EDS spectrum is as shown inFigure 5 As shown in Figure 5 It can be seen that the spectrum peaks of Sr, Zr and S elements are shown;

[0045] The temperature-dependent thermoelectric properties of the sample were analyzed, and the results are shown in Figure 6 As shown in Figure 6 It can be seen that the Seebeck coefficient of the sample reaches-475.5 μVK −1 at 323 K, the thermal conductivity is 2.2 Wm −1 K −1 , and it has a significant thermoelectric effect and low thermal conductivity.

[0046] Example 2, a β-SrZrS3 thermoelectric conversion bulk material, the preparation method comprising the following steps:

[0047] (1) Spread the 325 mesh SrZrO3 powder on the bottom of the crucible, place the crucible in the middle of the tube furnace, use a mechanical pump to vacuum to <0.1 Pa, introduce CS2 gas from one end of the tube furnace, control the gas flow at 60 SCCM, adjust the valve to keep the gas pressure at 80 Pa, set the temperature rising curve to heat the furnace body to 1200℃, and keep it for 1 h, naturally cool the furnace body to room temperature, and get a red-brown SrZrS3 powder precursor;

[0048] (2) After the SrZrS3 powder precursor is uniformly ground in a mortar, it is loaded into a graphite mold, the graphite mold is placed in a rapid sintering furnace, vacuum is extracted, and then rapid hot-pressing sintering is carried out (pressure 50 MPa, temperature 1300℃, holding time 5 min), and a β-SrZrS3 bulk material is obtained.

[0049] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing a β-SrZrS3 thermoelectric conversion bulk material, characterized by, The method comprises the following steps: (1) placing SrZrO3 powder in a tube furnace and vacuumizing; (2) introducing CS2 gas into the furnace, wherein the flow rate of the CS2 gas is 35-60 SCCM; (3) heating the tube furnace and keeping the temperature, and obtaining β-SrZrS3 powder after cooling to room temperature; (4) pre-pressing the β-SrZrS3 powder in a mold, and then placing the mold in a rapid hot-pressing sintering furnace and vacuumizing; (5) controlling the temperature in the furnace to reach 1300℃, keeping the temperature for 5 min, and cooling to room temperature under a pressure of 50 MPa, thereby obtaining a pure phase of β-SrZrS3 thermoelectric conversion bulk material.

2. The method of producing a β-SrZrS3 thermoelectric conversion bulk material according to claim 1, characterized by, In step (3), the tube furnace is heated to 1000-1200℃, the internal gas pressure is 35-80 Pa, and the temperature is kept for 1-12 h.

3. The method of producing a β-SrZrS3 thermoelectric conversion bulk material according to claim 1, characterized by, In step (4), the mold is a graphite mold.

4. A β-SrZrS3 thermoelectric conversion bulk material, characterized by, The material is prepared by the method as described in any one of claims 1-3.

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