CN103436724A - A new method for rapid preparation of high-performance PbS1-xSex-based thermoelectric materials - Google Patents

Abstract

The invention relates to a new method for rapidly preparing high-performance PbS _1-x Se _x- based thermoelectric materials, which comprises the following steps: 1) Weighing Pb powder according to the stoichiometric ratio of each atom of PbS _1-x+y Se _x+z , S powder and Se powder are used as raw materials, where when 0≤x﹤1.0, y=0.02, z=0; when x=1.0, y=0, z=0.02, and then the powder raw materials are ground and mixed evenly and pressed into block; 2) Initiate a self-propagating reaction on the block obtained in step 1), and cool naturally after the reaction is completed, and a single-phase PbS _{1-x Sex} solid solution can be obtained; 3) Grinding the PbS _{1-x Sex} solid solution obtained above into powder, and subjected to spark plasma activation sintering to obtain high-performance PbS _1-x Se _x- based thermoelectric materials. The invention has the advantages of fast reaction speed, simple process, high efficiency, energy saving and good repeatability, and the whole preparation process can be completed within 0.5 hours.

Description

A new method for rapid preparation of high-performance PbS1-xSex-based thermoelectric materials

technical field

The invention belongs to the technical field of preparation of new energy materials, and in particular relates to a new method for rapidly preparing high-performance PbS _1-x Se _x- based thermoelectric materials.

Background technique

The development of new and efficient energy conversion materials and technologies can alleviate the increasing damage to the natural environment and the depletion of fossil energy. At present, many scientists around the world are focusing their attention on finding and developing thermoelectric conversion technology—a renewable new energy conversion technology.

Thermoelectric conversion technology can realize direct mutual conversion between electric energy and thermal energy through the Seebeck effect and Peltier effect of thermoelectric materials. As an environmentally friendly energy conversion technology, it has great potential in recycling industrial waste heat and waste heat, and automobile exhaust gas. important application prospects. At the same time, it also has the advantages of no transmission parts, small size, no noise, and good reliability. The conversion efficiency of thermoelectric materials is mainly determined by the thermoelectric figure of merit ZT , ZT = a ² s T / k , where a is the Seebeck coefficient, s is the electrical conductivity, k is the thermal conductivity, and T is the absolute temperature.

Thermoelectric materials based on PbS _{1-x Sex} have better electrical properties and lower thermal conductivity, so they have higher ZT values. At the same time, it has the advantages of abundant raw material reserves and low prices.

At present, the method of preparing PbS _1-x Se _x- based thermoelectric materials mainly adopts the melting method. However, the temperature required for the melting method is high (>1100°C), while the melting points of the elements themselves are very low, such as Pb (327°C), S (115°C) and Se (221°C), which may cause the loss of element volatilization, and at the same time The required reaction time is longer, therefore, there are certain deficiencies in terms of high efficiency and energy saving. Therefore, a simple, quick, low energy consumption, and reproducible synthesis method is very important for the preparation of PbS _1-x Se _x- based thermoelectric materials.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for rapidly preparing high-performance PbS _1-x Se _x- based thermoelectric materials for the above-mentioned deficiencies in the prior art. The reaction speed is fast, the process is simple, and the repeatability is good. The prepared PbS _{1-xSex -} based dense bulk thermoelectric materials have excellent thermoelectric properties.

The technical scheme that the present invention adopts for solving the above-mentioned problem is:

A new method for rapidly preparing high-performance PbS _1-x Se _x- based thermoelectric materials, which includes the following steps:

1) Weigh Pb powder, S powder, and Se powder as raw materials according to the stoichiometric ratio of each atom of PbS _1-x+y Se _x+z , where when x is greater than or equal to 0 and less than 1.0 (that is, 0≤x﹤1.0), y=0.02, z=0; when x=1.0, y=0, z=0.02, then grind and mix the raw material powders evenly, then grind and mix them evenly, and press the evenly mixed powders into blocks;

2) After the self-propagating high-temperature synthesis (SHS, Self-propagating High-temperature Synthesis) reaction of the block obtained in step 1) is completed, the single-phase PbS _{1-x Sex} compound can be obtained;

3) Grinding the above-mentioned products into powder and performing discharge plasma activated sintering (PAS, Plasma Activated Sintering) to obtain high-performance PbS _1-x Sex _- based thermoelectric materials.

In the above scheme, the mass purity of Pb powder, S powder and Se powder in the step 1) is not less than 99.9%.

In the above solution, the self-propagating reaction in step 2) is to heat the end of the block to initiate the reaction.

In the above solution, the self-propagating reaction in step 2) uses an air atmosphere or a vacuum atmosphere or an inert gas atmosphere.

In the above scheme, the process of step 3) powder sintering by discharge plasma activation is as follows: the powder is packed into a graphite mold with a diameter of 15mm for compaction, and then sintered under the conditions of a vacuum of less than 10Pa and a sintering pressure of 35MPa, so as to The temperature was raised to 550°C at a heating rate of 100°C/min, and the sintering and densification time was 7 minutes.

The above preparation method has obtained a high-performance PbS _1-x Se _x based dense bulk thermoelectric material. At x=0, the thermoelectric performance figure of merit ZT reaches 0.5 at 875K.

Based on the above content, without departing from the basic technical idea of the present invention, according to the common technical knowledge and means in this field, the content can also be modified, replaced or changed in various forms, such as the self-propagating reaction atmosphere can be Replace it with other inert gases that do not react with Pb powder, S powder and Se powder.

The present invention needs to provide necessary energy to the raw material to induce thermochemical reaction to form a combustion wave, and the subsequent reaction continues with the support of the heat released by the previous reaction, and the required PbS _1-x Sex _- based thermoelectric reaction is formed after the reaction spreads. Material powder.

Compared with the existing PbS _{1-x Sex} preparation method, the advantages of the present invention are:

First, the present invention uses self-propagating high-temperature synthesis technology for the first time to prepare PbS _1-x Se _x- based thermoelectric materials, which have the advantages of fast reaction speed, simple equipment, good repeatability, high efficiency and energy saving, and fast heating and cooling rates;

Second, the present invention can prepare a PbS _1-x Se _x -based dense bulk thermoelectric material within 0.5 h, and the cost of raw materials is low.

Description of drawings

Fig. 1 is the XRD patterns of the powder after SHS and the block after PAS in Example 1.

Fig. 2 is the powder XRD pattern after SHS in embodiment 2.

Fig. 3 is the XRD patterns of the powder after SHS and the block after PAS in Example 3.

Fig. 4 is the powder XRD pattern after SHS in embodiment 4.

Fig. 5 is the powder XRD pattern after SHS in embodiment 5.

Figure 6(a) is the XRD pattern of the powder after SHS and the block after PAS; Figure 6(b) is the SEM image of the powder after SHS in step 2) (5.00 k times and 10.00 k times from left to right); Figure 6(c) is a graph showing the relationship between the dimensionless thermoelectric figure of merit ZT of the sintered block and the highest thermoelectric figure of merit ZT of the material prepared by the melting method as a function of temperature.

Detailed ways

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

In the following examples, the mass purity of Pb powder, S powder and Se powder is not less than 99.9%. In the drawings of the description, the products obtained by self-propagating reaction (SHS) are marked with "SHS", and the products obtained by discharge plasma activated sintering (PAS) are marked with "PAS".

Example 1

A new method for rapidly preparing high-performance PbS _1-x Se _x- based thermoelectric materials, which includes the following steps:

1) Weigh Pb powder and Se powder according to the stoichiometric ratio of each atom in the chemical formula PbSe _(1+0.02) (that is, x=1.0, y=0, z=0.02 in PbS _{1-x +} y Se x+z) Raw materials (note: the excess of Se is 2%, that is, the value of z is to compensate for the volatilization loss of Se in the reaction), the total mass is 4.5g, and then they are ground and mixed evenly, and the uniformly mixed powder is pressed into a diameter of 10mm Cylindrical block (pressing process: first hold pressure at 5MPa for 5min, then hold pressure at 8MPa for 10min);

2) End-ignite the block obtained in step 1) in an air atmosphere to initiate a self-propagating reaction (SHS) and cool naturally after the reaction is completed;

3) Grind the above-mentioned product into powder, put the powder into a 15mm graphite mold for compaction, and then conduct discharge plasma activation sintering (PAS) under the conditions of a vacuum of less than 10Pa and a sintering pressure of 35MPa, at a temperature of 100°C/min The heating rate was raised to 550° C., and the sintering and densification time was 7 minutes to obtain a PbSe dense bulk thermoelectric material.

It can be seen from Figure 1 that the products obtained after self-propagating reaction (SHS) and discharge plasma activation sintering (PAS) are all single-phase PbSe compounds.

Example 2

A new method for rapidly preparing high-performance PbS _1-x Se _x- based thermoelectric materials, which includes the following steps:

1) Weigh Pb powder and S powder according to the stoichiometric ratio of each atom in PbS _{(0.2+0.02) Se 0.8} (that is, x=0.8, y=0.02, z=0 in PbS 1- _x +y Se x+z) , Se powder as raw material (Note: S excess of 2%, that is, the value of y, is to compensate for the volatilization loss of S in the reaction), the total mass is 4.5g, and then they are ground and mixed evenly, and the evenly mixed powder is pressed into Cylindrical block with a diameter of 10mm (the pressing process is: first hold the pressure at 5MPa for 5min, and then hold the pressure at 8MPa for 10min);

2) End-ignite the block obtained in step 1) in an air atmosphere to initiate a self-propagating reaction (SHS) and cool naturally after the reaction is completed;

3) Grinding the above obtained product into powder for XRD test.

It can be seen from Figure 2 that the product obtained after the self-propagating reaction (SHS) is a single-phase PbS _0.2 Se _0.8 solid solution.

Example 3

A new method for rapidly preparing high-performance PbS _1-x Se _x- based thermoelectric materials, which includes the following steps:

1) Weigh Pb powder and S powder according to the stoichiometric ratio of each atom in PbS _{(0.4+0.02) Se 0.6} (that is, x=0.6, y=0.02, z=0 in PbS 1- _x +y Se x+z) , Se powder as the raw material (note: the excess of S is 2%, to compensate for the volatilization loss of S in the reaction), the total mass is 4.5g, and then they are ground and mixed evenly, and the evenly mixed powder is pressed into a cylindrical shape with a diameter of 10mm Block block (pressing process: first hold pressure at 5MPa for 5min, then hold pressure at 8MPa for 10min);

2) End-ignite the block obtained in step 1) in an air atmosphere to initiate a self-propagating reaction (SHS) and cool naturally after the reaction is completed;

3) Grind the above-mentioned product into powder, put the powder into a 15mm graphite mold for compaction, and then conduct discharge plasma activation sintering (PAS) under the conditions of a vacuum of less than 10Pa and a sintering pressure of 35MPa, at a temperature of 100°C/min The heating rate was raised to 550° C., and the sintering and densification time was 7 minutes to obtain a PbSe dense bulk thermoelectric material.

It can be seen from Figure 3 that the products obtained after self-propagating reaction (SHS) and discharge plasma activation sintering (PAS) are all single-phase PbS _0.4 Se _0.6 solid solutions.

Example 4

A new method for rapidly preparing high-performance PbS _1-x Se _x- based thermoelectric materials, which includes the following steps:

1) Weigh Pb powder and S powder according to the stoichiometric ratio of each atom in PbS ( _{0.6 +0.02)} Se _0.4 (that is, x=0.4, y=0.02, z=0 in PbS _1-x +y Se x+z) , Se powder as the raw material (note: the excess of S is 2%, to compensate for the volatilization loss of S in the reaction), the total mass is 4.5g, and then they are ground and mixed evenly, and the evenly mixed powder is pressed into a cylindrical shape with a diameter of 10mm Block block (pressing process: first hold pressure at 5MPa for 5min, then hold pressure at 8MPa for 10min);

2) End-ignite the block obtained in step 1) in an air atmosphere to initiate a self-propagating reaction (SHS) and cool naturally after the reaction is completed;

3) Grinding the above obtained product into powder for XRD test.

It can be seen from Figure 4 that the product obtained after the self-propagating reaction (SHS) is a single-phase PbS _0.6 Se _0.4 solid solution.

Example 5

A new method for rapidly preparing high-performance PbS _1-x Se _x- based thermoelectric materials, which includes the following steps:

1) Weigh Pb powder and S powder according to the stoichiometric ratio of each atom in PbS _{(0.8+0.02) Se 0.2} (that is, x=0.2, y=0.02, z=0 in PbS 1- _x +y Se x+z) , Se powder as a raw material, the total mass is 4.5g, then they are ground and mixed evenly, and the uniformly mixed powder is pressed into a cylindrical block with a diameter of 10mm (the pressing process is: first hold the pressure at 5MPa for 5min, and then press at 8MPa Hold pressure for 10 minutes);

2) End-ignite the block obtained in step 1) in an air atmosphere to initiate a self-propagating reaction (SHS) and cool naturally after the reaction is completed;

3) Grinding the above obtained product into powder for XRD test.

It can be seen from Figure 2 that the product obtained after the self-propagating reaction (SHS) is a single-phase PbS _0.8 Se _0.2 solid solution.

Example 6

A new method for rapidly preparing high-performance PbS _1-x Se _x- based thermoelectric materials, which includes the following steps:

1) Weigh Pb powder and S powder as raw materials according to the stoichiometric ratio of each atom in PbS _(1+0.02) (that is, x=1, y=0, z=0.02 in PbS _1- x ₊ y Se x+z) , the total mass is 4.5g, and then they are ground and mixed evenly, and the uniformly mixed powder is pressed into a cylindrical block with a diameter of 10mm (the pressing process is: first hold the pressure at 5MPa for 5min, and then hold the pressure at 8MPa for 10min);

2) End-ignite the block obtained in step 1) in an air atmosphere to initiate a self-propagating reaction (SHS) and cool naturally after the reaction is completed;

3) Grind the above-mentioned product into powder, put the powder into a 15mm graphite mold for compaction, and then conduct discharge plasma activation sintering (PAS) under the conditions of a vacuum of less than 10Pa and a sintering pressure of 35MPa, at a temperature of 100°C/min The heating rate was increased to 550°C, and the sintering and densification time was 7 minutes to obtain a PbS dense bulk thermoelectric material.

Figure 6(a) is the XRD pattern of the product powder after self-propagating reaction (SHS) and the bulk product after spark plasma activation sintering (PAS); Figure 6(b) is the SEM image of the powder after SHS in step 2) (from Zoom in 5.00 k times and 10.00 k times from left to right respectively); Figure 6(c) is the relationship between the dimensionless thermoelectric figure of merit ZT of the bulk after PAS and the highest thermoelectric figure of merit ZT of the material prepared by the comparative melting method as a function of temperature .

It can be seen from Figure 6 that the product obtained after SHS is a single-phase PbS compound, and its powder grain size distribution is wide; after PAS, the obtained block is a single-phase PbS compound. In the above temperature range, the average ZT value is higher than that of the comparative example. At the same time, when the temperature is 875K, it can reach ZT ~0.57, which is nearly 100% higher than that of the comparative example.

comparative example

Melting method process: Pb powder and S powder are used as raw materials, mixed according to the molar ratio of 1:1, raised from room temperature to 1100°C at a constant speed (the time for constant temperature rise is 12h), and kept at 1100°C for 6h, then PAS sintering, PAS The process is: the vacuum is less than 10Pa, the sintering pressure is 35MPa, the temperature is raised to 550°C at a heating rate of 100°C/min, and the sintering densification time is 7min. the

Claims (7)

1. one kind prepares high-performance PbS fast _1-xse _xthe novel method of base thermoelectricity material is characterized in that it comprises the following steps:

1) press PbS _1-x+yse _x+zthe stoichiometric ratio of each atom takes Pb powder, S powder and Se powder as raw material, wherein when 0≤x ﹤ 1.0, and y=0.02, z=0; When x=1.0, y=0, z=0.02, then be pressed into block by the powder stock ground and mixed after evenly;

2) step 1) gained block is caused to self-propagating reaction, reacted rear naturally cooling, obtain single-phase PbS _1-xse _xsosoloid;

3) by above-mentioned gained PbS _1-xse _xthe sosoloid grind into powder, carry out discharge plasma activated sintering, obtains high-performance PbS _1-xse _xbase thermoelectricity material.

2. a kind of quick preparation high-performance PbS according to claim 1 _1-xse _xthe novel method of base thermoelectricity material, is characterized in that the quality purity of Pb powder in described step 1), S powder and Se powder all is not less than 99.9%.

3. a kind of quick preparation high-performance PbS according to claim 1 _1-xse _xthe novel method of base thermoelectricity material, is characterized in that described step 1) pressing process is: the first step, pressurize 5min under 5MPa; Second step, pressurize 10min under 8MPa.

4. a kind of quick preparation high-performance PbS according to claim 1 _1-xse _xthe novel method of base thermoelectricity material, is characterized in that described step 2) in self-propagating reaction the block end is heated to initiation reaction.

5. a kind of quick preparation high-performance PbS according to claim 1 _1-xse _xthe method of base thermoelectricity material, is characterized in that described step 2) in use air atmosphere or vacuum atmosphere or inert gas atmosphere in self-propagating reaction.

6. a kind of quick preparation high-performance PbS according to claim 1 _1-xse _xthe novel method of base thermoelectricity material, it is characterized in that the process that powder in described step 3) carries out discharge plasma activated sintering is: by the powder compacting in the graphite jig that diameter is 15mm of packing into, then be less than 10Pa and sintering pressure is to carry out sintering under the 35MPa condition in vacuum, temperature rise rate with 100 ℃/min is warmed up to 550 ℃, sintering densification time 7min.

7. the described preparation method of claim 1 obtains high-performance PbS _1-xse _xbase compact block thermoelectric material.

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