Preparation method of cubic structure CoSbS thermoelectric compound

A cubic structure and compound technology, which is applied in the field of preparation of CoSbS-based thermoelectric materials, can solve the problems of high overall cost, inability to obtain high symmetry cubic structure thermoelectric materials, high cost of Sb single substance, etc., and achieve cheap constituent elements and crystal structure symmetry Controllable, short material cycle results

Inactive Publication Date: 2019-04-16

HENAN POLYTECHNIC UNIV

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AI-Extracted Technical Summary

Problems solved by technology

[0004] CoSb 3 The high symmetry is determined by its molecular structure, and its crystal system itself has high symmetry, but the cost of Sb is very high, resulting in the corresponding CoSb 3 overall high cost

However, f...

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Method used

As shown in Fig. 4 and 5, suitable doping amount helps to improve the thermoelectric performance of CoSbS material, and reason mainly is: the doping of Ni may cause part Ni to occupy the position of Co in lat...

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Abstract

The invention provides a preparation method of a cubic structure CoSbS thermoelectric compound. The method comprises the steps that 1), raw materials are placed in a ball milling jar, the raw materials comprise Co powder, Sb powder and S powder which are mixed according a certain mole ratio; 2), wet process ball milling; 3), products obtained after wet-process ball milling is conducted are dried to obtain a dried powder precursor; 4), the obtained powder precursor is pressed into a block; 5), high-pressure synthesis is conducted on the pressed block to obtain the cubic structure CoSbS compound, wherein the high-pressure synthesis in step 5) is conducted on a high-temperature high-pressure device, the synthesis process comprises the steps that a block sample is wrapped with a boron nitrideinsulation tube and put into a pyrophyllite synthesis block to be synthesized under high pressure, and the adopted synthesis pressure is greater than 2 GPa. The method has the advantages that the cubic structure CoSbS thermoelectric compound can be effectively obtained, the technology is simple, and the cycle is short.

Application Domain

Selenium/tellurium compounds with other elementsCobalt compounds +1

Technology Topic

High pressureMole ratio +4

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Examples

Experimental program(4)

Example Embodiment

[0045] Example 1

[0046] In this embodiment, taking the process of preparing CoSbS as an example, the preparation method of the thermoelectric material of the present invention is described in detail.

[0047] Such as figure 1 As shown, the method includes the following steps: 1) batching step; 2) wet ball milling step; 3) drying step; 4) pressing step; 5) sintering step.

[0048] The five steps above will be described in detail below.

[0049] 1) Ingredient steps

[0050] Take Co, Sb, and S as raw materials, mix them in the molar ratio of the molecular formula of CoSbS, and place them in a stainless steel ball mill tank. Preferably, the raw materials are Co powder, Sb powder and S powder with a purity of ≥99.5%; the raw materials are weighed according to the CoSbS stoichiometric ratio, and the total weight is 5g. The ball to material ratio can be set to 20:1.

[0051] Preferably, in order to increase the possibilities of the CoSbS-based thermoelectric material, Ni, Se, Te or Fe can be added to the raw material, and the doping amount ranges from 5 to 100% of Co.

[0052] 2) Wet grinding

[0053] Before wet milling the raw materials added to the ball milling tank, the raw materials usually need to be deoxygenated and/or protected. Deoxygenation and/or protection treatment includes evacuating the ball milling tank and introducing high-purity Ar gas, and then repeating the operation of vacuuming and passing high-purity Ar for several times, such as 3-5 times, to ensure exhaustion of oxygen in the ball milling tank .

[0054] After the deoxygenation treatment, the treated ball mill tank is fixed on a ball mill (for example, a planetary ball mill), and wet ball milling is performed at a predetermined rotation speed for a predetermined period of time. The predetermined rotation speed mentioned here is preferably 300 rpm, and the predetermined time period is preferably 240 minutes.

[0055] 3) Dry

[0056] After the wet milling, the samples in the ball milling tank are collected, and then the wet milled product is dried and dried in a vacuum for a period of time to volatilize all the organic liquid (alcohol) to obtain a dry powder. In this embodiment, the drying process used is: placing the wet-milled product in a vacuum drying oven and vacuum drying for 5-10 hours at a drying temperature of 50-70°C, preferably 60°C.

[0057] 4) Suppression

[0058] The dried product is placed in a mold and compressed into a block using a tablet press.

[0059] 5) Sintering

[0060] Finally, the pressed block is pressure-sintered to obtain a compact CoSbS block thermoelectric material. Preferably, the sintering pressure used in the sintering process is 1-4 GPa. The sintering temperature is 950-1150°C, the heating rate is (100-200°C/min), and the sintering time is 30min. The purity prepared under this condition is high, see the specific X-ray diffraction structure figure 1. From figure 1 It can be seen that the critical split point of orthogonal structure and cubic structure appears at 3GPa. Samples below 3GPa (not included) have orthogonal structure and are consistent with the structure prepared by conventional mechanical alloying or vacuum melting methods. Pressure samples of 3GPa and above It is a cubic structure with better symmetry, that is, the applicant has discovered that for the preparation of the critical segmentation point (or segmentation area) of the CoSbS-based thermoelectric material, a cubic structure of CoSbS-based thermoelectricity can be obtained at a preparation pressure higher than the critical segmentation area material.

Example Embodiment

[0061] Example 2

[0062] In this embodiment, the thermoelectric material Ni is prepared x Co 1-x SbS (x=0-0.15).

[0063] In the preparation of thermoelectric material Ni x Co 1-x In the SbS process, the inventors adopted steps similar to those in Example 1, namely 1) batching step; 2) wet ball milling step; 3) drying step; 4) pressing step; 5) sintering step. The sintering pressure is 1~3GPa. The sintered samples have been tested by X-ray diffraction, and it is found that all samples have an orthogonal structure under 1GPa conditions (such as figure 2 ), the sample changes into a cubic structure after doping with 5% Ni under 2GPa conditions (such as image 3 ), that is, Ni doping can reduce the structural transition pressure of CoSbS.

[0064] In order to characterize the performance of samples with different structures, Ni-doped samples synthesized from 1 GPa and 3 GPa were cut and polished, and the resistivity, Seebeck coefficient and thermal conductivity of the samples were tested with LSR-3/CTA-3 and LFA-457. And calculated the quality factor.

[0065] Such as Figure 4 with 5 As shown, a proper doping amount helps to improve the thermoelectric performance of CoSbS materials. The main reason is: Ni doping may cause part of Ni to occupy the position of Co in the crystal lattice, forming a donor impurity level, thereby increasing the current carrying capacity of CoSbS The sub-concentration reduces the resistivity, and at the same time Ni replaces Co to cause lattice distortion and reduce the thermal conductivity.

[0066] Such as Figure 4 As shown, the orthogonal structure Ni x Co 1-x The maximum quality factor of SbS is 0.32 (x=0.05, @773K), while the cubic structure of Ni x Co 1-x The maximum quality factor of SbS ( Figure 5 ) Is 0.37 (x=0.1, @773K). The higher thermoelectric performance of the cubic structure sample can be attributed to the higher electrical transport performance contributed by its high crystal structure symmetry (the maximum power factor of the cubic structure sample is 17.6uWcm -1 K -2 , And the maximum power factor of the square structure sample is only 14.0uWcm -1 K -2 ).

Example Embodiment

[0067] Example 3

[0068] In this embodiment, the thermoelectric material Fe is prepared x Co 1-x SbS (x=0-0.1).

[0069] In the preparation of thermoelectric material Fe x Co 1-x In the SbS process, the inventors adopted steps similar to those in Example 1, namely 1) batching step; 2) wet ball milling step; 3) drying step; 4) pressing step; 5) sintering step.

[0070] In this embodiment, the sintering pressure is 2 GPa. Image 6 For the X-ray diffraction pattern of the sample, it is found that the Fe-doped CoSbS sample still has an orthogonal structure, that is, Fe doping cannot reduce the crystal structure transition pressure of CoSbS like Ni. Because Fe doping does not improve the symmetry of the crystal structure of CoSbS, and at the same time, to provide more electrons to the CoSbS compound, the resistivity of the sample increases and the thermoelectric performance decreases (the power factor of Fe doped CoSbS at room temperature is only 5×10 -5 μWcm -1 K -2 ).

[0071] Similarly, the applicant uses P x Co 1-x SbS conducted a similar experiment and found that P doping has an orthogonal structure at 2Gpa, which cannot reduce the crystal structure transition pressure.

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Lithium ion battery pack state-of-health evaluation method and lithium ion battery pack state-of-health evaluation system

ActiveCN105607004AImprove the environmentEnergy savingElectrical testingData processingLithium ion battery pack

Owner:BEIJING PRIDE NEW ENERGY BATTERY

Preparation method of cubic structure CoSbS thermoelectric compound

AI-Extracted Technical Summary

Problems solved by technology

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Abstract

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Examples

Example Embodiment

Example Embodiment

Example Embodiment

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Description & Claims & Application Information

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