Preparation method of organic compound composite doped Ag2Se-based thermoelectric material

Abstract

The application discloses a preparation method of an organic compound doped Ag2Se-based thermoelectric material, and belongs to the technical field of thermoelectric materials. 20 H 30 O2 into a mortar and mix uniformly; the uniformly mixed powder is cold-pressed into a block; the cold-pressed block is subjected to high-temperature and high-pressure synthesis, and an organic compound doped Ag2Se-based thermoelectric material is obtained after shaping. According to the preparation method, the Ag powder, the Se powder and the organic compound CHO are mixed uniformly in proportion, cold-pressed, placed in an assembled cavity, and subjected to high-temperature and high-pressure one-step synthesis, so that the method is simple, easy to control and remarkable in effect; the thermal conductivity of the material is effectively reduced; the thermal conductivity is changed by adjusting the content of the organic compound, and the thermoelectric performance is finally optimized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermoelectric materials, and particularly relates to a preparation method of an organic compound doped Ag2Se-based thermoelectric material. BACKGROUND

[0002] The modernization of the world economy has brought great convenience to people's life, and under the rapid development of economy, energy plays the most important role. In the process of using traditional energy, the environmental problems related to it also come. Most of the energy is released in the form of heat energy in the process of energy combustion, automobile exhaust emission, etc., causing energy waste. In the face of new energy situation and climate change, the idea of sustainable development has become the consensus of the international community. Promoting energy transformation, realizing green and low-carbon development, and developing and utilizing renewable energy have become the mission of global human beings. In the wave of green energy development, thermoelectric conversion technology has developed rapidly due to its unique advantages and plays an irreplaceable role in many renewable energies.

[0003] Thermoelectric conversion technology is a new energy utilization technology, which can realize the direct conversion of heat energy and electric energy, and is therefore considered as a candidate material to alleviate the pressure of fossil fuel consumption and environmental pollution. After assembling P-type and N-type thermoelectric materials, a thermoelectric device can be prepared, and the thermoelectric device can realize temperature difference power generation by converting heat energy into electric energy. In this conversion process, the waste heat in industrial production, automobile exhaust and environment can be fully utilized, and then converted into electric energy with higher utilization value. Thermoelectric materials can play a positive role in improving energy crisis, environmental pollution and other problems. Thermoelectric materials are divided into three categories: near-room-temperature thermoelectric materials, medium-temperature thermoelectric materials and high-temperature thermoelectric materials. Near-room-temperature thermoelectric materials have good thermoelectric properties in the low-temperature region, and Bi2Te3 is a common near-room-temperature thermoelectric material. However, Te is toxic and expensive, so a cheap, non-toxic and good thermoelectric material needs to be found to replace Bi2Te3. Researchers have found that Ag2Se has good thermoelectric properties at low temperatures. Ag2Se is an n-type narrow-band-gap semiconductor with high electron mobility, good intrinsic sigma and low kappa L , and shows good thermoelectric properties near room temperature. In addition, Ag2Se can be made into flexible thermoelectric devices. In addition, the composition elements Ag and Se of Ag2Se have higher crust abundance than Bi and Te, are environmentally friendly, and bulk Ag2Se has better mechanical properties, which is expected to replace the most widely studied Bi2Te3-based near-room-temperature thermoelectric material in the room temperature range, and promote the development of room-temperature thermoelectric materials and devices.

[0004] The intrinsic thermal conductivity of Ag2Se is relatively low, but the total thermal conductivity is high, and the thermal conductivity increases with the increase of temperature, if the thermal conductivity is further reduced, the high zT value can be obtained under the condition of little electrical reduction. At present, the synthesis methods of Ag2Se mainly focus on hydrothermal method, solvothermal method and the like, and strict experimental conditions and experimental environment are usually required in the experimental process. Moreover, organic solvents are usually used to complete, most of the organic solvents are toxic and can pollute the environment, therefore, it is of great significance to find a green, energy-saving and efficient method to prepare Ag2Se material. SUMMARY

[0005] In view of the problems existing in the Ag2Se-based thermoelectric material at the present stage, the application provides a preparation method of an organic compound doped Ag2Se-based thermoelectric material, the required product can be obtained after high-temperature and high-pressure treatment of Ag powder, Se powder and CHO organic compound, the preparation method is simple, easy to control and has remarkable effect, and the thermal conductivity is effectively reduced; the carrier concentration and carrier mobility of the Ag2Se-based material are changed by adjusting the content of the composite organic compound, and the thermal performance is further optimized by the composite CHO organic compound, so that the optimal performance is achieved.

[0006] The technical scheme of the application is as follows:

[0007] The application provides a preparation method of an organic compound doped Ag2Se-based thermoelectric material, comprising the following steps:

[0008] (1) Ag powder, Se powder and organic compound C 20 H 30 O2 are put into a mortar and mixed uniformly to obtain uniformly mixed powder;

[0009] (2) the uniformly mixed powder in step (1) is cold-pressed into a block;

[0010] (3) the block cold-pressed in step (2) is subjected to high-temperature and high-pressure synthesis, and the organic compound doped Ag2Se-based thermoelectric material is obtained after shaping.

[0011] Further, the molar ratio of Ag to Se in step (1) is 1.97-2:1.

[0012] Further, the organic compound C 20 H 30 O2 accounts for 0.1-2wt.% of the total mass of Ag and Se in step (1).

[0013] Further, the molar ratio of Ag to Se in step (1) is 2:1 or 1.97:1.

[0014] Further, the organic compound C 20 H30 O2 is 1 wt.% of the total mass of Ag and Se.

[0015] Further, the C 20 H 30 O2, Ag powder and Se powder are mixed in a glove box for more than 1 h by using agate to ensure uniform mixing.

[0016] Further, the cold pressing forming oil pressure in step (2) is 2 MPa, and the holding time is 15 s.

[0017] Further, the pressure of the high temperature and high pressure in step (3) is 1-5 GPa, the temperature is 300-900 DEG C, the holding time is 30 min, and the high temperature and high pressure synthesis is rapidly reduced to room temperature after being completed.

[0018] Further, the pressure of the high temperature and high pressure in step (3) is 1 GPa, the temperature is 700 DEG C, the holding time is 30 min, and the high temperature and high pressure synthesis is rapidly reduced to room temperature after being completed.

[0019] The application also provides the organic compound doped Ag2Se-based thermoelectric material prepared by the preparation method.

[0020] The application has the following beneficial effects:

[0021] The preparation method of the organic compound doped Ag2Se-based thermoelectric material provided by the application can be synthesized by mixing Ag powder, Se powder and CHO organic compound manually and through high temperature and high pressure.

[0022] 1. The preparation material has a short cycle and a simple process. The application has a simple process, rapid reaction time, cost saving and is suitable for industrial production.

[0023] 2. The prepared bulk material has good density. The electrical conductivity is high, and the thermal conductivity is low, so that the thermoelectric performance is good. The minimum thermal conductivity value is reduced to 0.5 Wm -1 K -1 Compared with the non-composite Ag2Se thermoelectric material, the zT value is greatly improved, and the zT max = 1.47. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 X-ray diffraction patterns of Ag2Se composite with different concentrations of C 20 H 30 O2 samples synthesized by high temperature and high pressure;

[0025] Figure 2 Thermoelectric performance diagrams of Ag2Se composite with different concentrations of C 20 H 30 O2 samples synthesized by high temperature and high pressure;

[0026] Figure 3 Ag2Se for high-temperature and high-pressure synthesis 1.97 Se with different concentrations of C 20 H 30 X-ray diffraction pattern of the O2 sample;

[0027] Figure 4 Ag2Se for high-temperature and high-pressure synthesis 1.97 Se with different concentrations of C 20 H 30 Scanning electron microscope image of the O2 sample;

[0028] Figure 5 Ag2Se for high-temperature and high-pressure synthesis 1.97 Se with different concentrations of C 20 H 30 Thermoelectric property diagram of the O2 sample. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the following described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] It should be understood that the experimental operations not described in detail in the experiment are conventional experimental operations well known to those skilled in the art.

[0031] In order to verify the performance of the obtained samples, the samples after high-pressure sintering are polished and cut, and the electrical and thermal properties of the samples are tested by using a China-made Cooray CTA-3s type thermoelectric material electrical property tester and a Germany Nierstein company produced model LFA457 laser thermal conductivity instrument respectively.

[0032] Embodiment 1

[0033] A preparation method of an organic compound composite doped Ag2Se-based thermoelectric material, comprising the following steps:

[0034] 1) batching: put Ag powder, Se powder and organic compound C 20 H 30 O2 into a marver. The raw materials are high-purity Ag powder (purity 99.99%), Se powder (purity 99.999%), C 20 H 30 O2 (purity 99.9%). The molar ratio of Ag powder to Se powder is 2:1, the total mass of Ag powder and Se powder is 4g, and the mass of C 20 H 30O2 is 0.1-2wt.% of the total mass of Ag powder and Se powder.

[0035] 2) Mixing: Before mixing, it is usually necessary to clean, dry and deoxidize the mortar. The raw materials of step (1) are manually mixed uniformly in a glove box, and the mixing time is 1h.

[0036] 3) Cold pressing: Put the uniformly mixed powder into a 12mm mold, and cold press it into a block using a powder tablet press, with a pressure of 2MPa and a holding time of 15s.

[0037] 4) High temperature and high pressure synthesis: The cold-pressed block is subjected to high temperature and high pressure synthesis, with a synthesis pressure of 1GPa, a synthesis temperature of 700℃, and a holding time of 30min. The complete and dense sample is obtained.

[0038] Figure 1 To synthesize Ag2Se composite C 20 H 30 The X-ray diffraction pattern of O2 can be observed, and the sample obtained after composite C 20 H 30 O2 is still a pure phase. Figure 2 The thermal conductivity of the sample obtained after composite C 20 H 30 O2 is reduced. The lowest thermal conductivity is 0.8Wm -1 K -1 , and the maximum zT value is 0.7, which is improved compared with pure Ag2Se.

[0039] Example 2

[0040] A preparation method of an organic compound composite doped Ag2Se-based thermoelectric material, comprising the following steps:

[0041] 1) Preparation: Put Ag powder, Se powder and organic compound C 20 H 30 O2 into a agate mortar. The raw materials are high-purity Ag powder (purity 99.99%), Se powder (purity 99.999%), and C 20 H 30 O2 (purity 99.9%). The molar ratio of Ag powder to Se powder is 1.97:1, the total mass of Ag powder and Se powder is 4g, and C 20 H 30 O2 is 0.1-2wt.% of the total mass of Ag powder and Se powder.

[0042] 2) Mixing: Before mixing, it is usually necessary to clean, dry and deoxidize the mortar. The raw materials of step (1) are manually mixed uniformly in a glove box, and the mixing time is 1h.

[0043] 3) Cold pressing: Place the evenly mixed powder into a 12mm mold and cold press it into a block using a powder tablet press. The pressure used is 2MPa, and the pressing time is 15s.

[0044] 4) High-temperature and high-pressure synthesis: The cold-pressed block is subjected to high-temperature and high-pressure synthesis at a pressure of 1 GPa, a temperature of 700℃, and a holding time of 30 min. A complete and dense sample is obtained.

[0045] Figure 3 Synthesis of Ag under high temperature and high pressure 1.97 Se compound C 20 H 30 The X-ray diffraction pattern of O2 shows that the composite C 20 H 30 The sample obtained after O2 treatment remains a pure phase.

[0046] Figure 4 Ag synthesized under high temperature and high pressure 1.97 Se compounded with different concentrations of C 20 H 30 Scanning electron microscopy (SEM) images of the O2 sample reveal numerous voids and a carbon second phase within the composite organic material. This phenomenon is attributed to the gas produced during the high-temperature, high-pressure decomposition of the organic matter, resulting in the presence of pores within the sample.

[0047] Figure 5 For Ag 1.97 Se compounded with different C 20 H 30 The thermoelectric performance test results of the O2 concentration sample showed that, due to the presence of pores, the composite C... 20 H 30 The thermal conductivity of the O2 sample was significantly lower than that of the uncomposite sample. This was especially true for the composite sample containing 1 wt.% C. 20 H 30 The electrical properties of the O2 sample decreased slightly, while the thermal conductivity decreased significantly, leading to a decrease in Ag. 1.97 Se compound C 20 H 30 The highest zT value of 1.47 was obtained with an O2 concentration of 1 wt.%.

[0048] Comparative Example 1

[0049] Compared to Example 1, the molar ratio of Ag to Se is 2:1 and no C is added. 20 H 30 O2, the rest of the operation is the same, see the specific results. Figure 2 This indicates that high temperature and high pressure can synthesize pure phase Ag2Se bulk materials, and the bulk materials obtain a zT value of 0.6.

[0050] Comparative Example 2

[0051] Compared with Example 2, the molar ratio of Ag and Se is 1.97:1 and no C is added 20 H 30 O2, the rest of the operation is the same, the specific results are shown in Table 2 Figure 5 It is shown that the Ag vacancy can reduce the carrier concentration, the absolute value of Seebeck coefficient increases, and the thermal conductivity decreases, resulting in the increase of zT value, and the maximum zT value is 1.1.

[0052] The above only is the embodiment of the present application, the specific material and the characteristic of the scheme known in the art and the common sense are not described too much here. It should be pointed out that the above embodiment is only used for helping understanding the core idea of the present application, for the person skilled in the art, without departing from the present application, a number of deformation and improvement can be made, according to the idea of the present application, in the specific implementation and application range will have the change, according to the above, the content of the specification should not be understood as the limitation of the present application.

Claims

1. A method for preparing an organic composite doped Ag₂Se-based thermoelectric material, characterized in that, Includes the following steps: (1) Mix Ag powder, Se powder and organic matter C 20 H 30 O2 is placed in a mortar and mixed thoroughly to obtain a uniformly mixed powder; the molar ratio of Ag to Se is 1.97~2:1; the organic compound C 20 H 30 O2 accounts for 0.1~2 wt.% of the total mass of Ag and Se; (2) The powder mixed evenly in step (1) is cold-pressed into a block; the cold pressing hydraulic pressure is 2 MPa and held for 15s; (3) The block cold-pressed in step (2) is subjected to high temperature and high pressure synthesis to obtain organic composite doped Ag2Se-based thermoelectric material after molding; the pressure of the high temperature and high pressure is 1-5 GPa, the temperature is 300-900 ℃, the holding time is 30 min, and the temperature is rapidly reduced to room temperature after the high temperature and high pressure synthesis is completed.

2. The preparation method according to claim 1, characterized in that, The molar ratio of Ag and Se in step (1) is 2:1 or 1.97:

1.

3. The preparation method according to claim 1, characterized in that, The organic compound C mentioned in step (1) 20 H 30 O2 accounts for 1 wt.% of the total mass of Ag and Se.

4. The preparation method according to claim 1, characterized in that, C mentioned in step (1) 20 H 30 O2, Ag powder, and Se powder were ground and mixed in a glove box with agate for more than 1 hour to ensure uniform mixing.

5. The preparation method according to claim 1, characterized in that, The high-temperature and high-pressure process in step (3) involves a pressure of 1 GPa, a temperature of 700 °C, and a holding time of 30 min. After the high-temperature and high-pressure synthesis is completed, the temperature is rapidly reduced to room temperature.

6. The organic composite doped Ag2Se-based thermoelectric material prepared by the preparation method according to any one of claims 1-5.

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