Method for preparation of silver antimony telluride thermoelectric material by combining low temperature solid phase reaction with hot pressing process

Technical Field

The invention belongs to the field of new energy materials, in particular to a low-temperature solid-phase reaction with antimony silver telluride hot-pressing process for preparing method of thermoelectric material.

Background Art

Thermoelectric power generation is to utilize the thermoelectric effect of the semiconductor material (Seebeck effect) the thermal energy is directly converted into electrical energy to be full static direct power generation mode. Thermoelectric power generation device typically has a device of simple structure, low-noise, wear-free, leak-free, long-term reliability, and the like. The thermoelectric power generation technology has been in the military, aerospace, medical, microelectronics and other fields have an important role. As the market for oil supply, such as the warming of the climate and increasingly prominent of environmental issues, temperature-difference power generating technology as an emerging green energy technologies are attracting more and more attention. In addition to the traditional application field, the current phase States Government and research institutions efforts are being made to the application of thermoelectric power generation technology areas to the solar energy photoelectric-thermoelectric composite power generation, industrial waste heat recovery and the automobile (including large oil tanker and the like surface ships and submarines) engine exhaust gas recycling. In domestic car, for example, fuel consumption of the engine in the energy of the generated, only about 30% for driving the vehicle and for the vehicle-mounted electric appliances, and about 40% of the waste heat energy in the form of exhaust gas discharge. According to the 2010 year automobiles and fuel oil consumption amount calculating, in order to exhaust the total energy of the waste heat is folded near million tons of oil, amounting to two-and-a-half daqing the yearly output of the oil.

P-type and the n-type thermoelectric materials of the thermoelectric device is a thermoelectric generating device of the core part, its conversion efficiency determines the conversion efficiency of thermoelectric power generation system. The conversion efficiency of the thermoelectric device depends on the performance Figure of merit ZT thermoelectric materials (material integrated thermoelectric performance characterization parameter) and system temperature differential. At present, commercial use of the room temperature of the thermoelectric material comprises bismuth telluride alloy and a middle-temperature use material of the lead telluride compound. Because of reasons known, commercial field of lead-containing compounds from the trend is not and change. In automobile exhaust gas, and industrial waste heat and other low-density heat source for the purposes of recycling, there is an urgent need to develop environmentally friendly alternative lead telluride material of the new material.

Antimony silver telluride (AgSbTe₂) is I-V-VI group compound "semiconductor" a. Due to their very low thermal conductivity and a relatively large Seebeck coefficient, AgSbTe₂ compounds of great concern is the International in one of warm materials system. In the known in the simple three-element compound, AgSbTe₂ has the highest thermoelectric Figure of merit (296 the when [...] ZT=1.66). It is worth noting that, the material in the room temperature to 450 the entire temperature interval [...] has a good thermoelectric transmission characteristic, this is the automobile exhaust gas, and industrial waste heat recovery using the corresponding temperature range.

Silver telluride with antimony normally adopts the traditional simple substance element molten, slow cooling or the area melts method for preparing. The reasons for its own nature of the material, the traditional method cannot be avoided in preparing sample containing micron scale silver telluride and other impurities. In recent years, researchers discovery and development of the process for preparing a plurality of new, includes an ultrasonic chemical method, high-energy ball milling, melt turns on lathe flings and method for a plurality of high temperature and high pressure. In terms of industrial production, the above method needs a long time or high-temperature smelting, or need special preparation device, are not conducive to mass production.

Content of the invention

The invention solves the technical problem that the disadvantages of the above-mentioned prior art by providing a low-temperature solid-phase reaction with antimony silver telluride hot-pressing process for preparing method of thermoelectric material, the reaction temperature is low, has simple and controllable process, the production cost is low, and the preparation of the antimony silver telluride block, the material density is high, good repeatability, high purity, excellent thermoelectric performance.

The invention is to solve the above-mentioned proposed problems, the invention adopts the technical scheme is:

Low temperature solid phase reaction process for preparing the hot pressing method of silver telluride antimony thermoelectric material, comprising the following steps:

1) proportioning: in accordance with the chemical formula AgSbTe_2+x of the each element in the weighing stoichiometric ratio of elemental silver, tellurium and stibium as a raw material, wherein for x 0-0.02;

2) block sealing: step 1) the raw materials are mixed, vacuum sealing body is pressed into blocks;

3) solid phase reaction: of the step 2) of the vacuum after sealing the block is heated to the reaction temperature 390-450 the insulation [...] 6-12h, single-phase to single-phase or near [...] antimony silver telluridesilver telluride antimony [...] ;

4) hot pressing: step 3) grinding [...] after the hot-pressing sintering, to obtain high-density silver telluride antimony thermoelectric material.

According to the above-mentioned scheme, step 1) the elemental silver, tellurium and stibium into the powder, particle size is preferably 200 mesh the following.

According to the above-mentioned scheme, step 1) the elemental silver, the purity of the tellurium and stibium greater than or equal to 99.5%.

According to the above-mentioned scheme, step 2) mixed in the conditions of: grinding the raw materials 30-60min.

According to the above-mentioned scheme, step 2) to the condition of medium pressure into block: the resulting bulk density silver telluride antimony density of not less than 85%. Wherein the size of the block obtained according to needs. The resulting block can be pressed into the diameter is 10-15mm, height is 4-6mm of the cylinder, and then vacuum-sealed in diameter 20-25mm the quartz tube.

According to the above-mentioned scheme, step 3) is not greater than the rate of rise in the 100 [...] /h, in order to avoid volatilization of raw materials after the sealed container is attached to the cold end of the (such as quartz tube), thereby influencing the stoichiometric ratio.

According to the above-mentioned scheme, step 3) in the in the heating process, heating up to the reaction temperature the following 50-100 the when [...] , reducing the rate of rise of temperature to not higher than the 50 [...] /h, in order to avoid temperature overshoot. The required reaction time a negative correlation with the reaction temperature. In the course of solid phase reaction, complete shape of the block to keep as far as possible, the sealing container wall (such as quartz tube) to non-volatile matter, if necessary, step 3) the resulting [...] repeat steps 2) and 3).

According to the above-mentioned scheme, step 3) in the hot-pressing sintering conditions: under vacuum or inert atmosphere, pressure of not less than 30 MPa, the temperature of hot the 400-480 [...] , time is 15-30min.

The above-mentioned method of preparing silver telluride antimony thermoelectric material, the relative density is greater than 96% (the theoretical density is 7.158g/cm³); in ZT thermoelectric performance index the 300 [...] of greater than 0.85, room temperature of not less than 0.25; wherein for x 0.02 time, the relative density is greater than 98.5%, the largest ZT thermoelectric performance index up to 1.10.

Compared with the prior art, the beneficial results of this invention are:

This invention utilizes the highly mature industry related art has been common and experimental equipment, to elemental Ag, Sb, Te powder as raw material, first of all through the low-temperature solid-on the contrary should be relatively low-density single-phase or near single-phase silver telluride[...] , then adopt the hot-pressing process, to obtain high-density silver telluride antimony bulk material, effectively save energy, reduce cost, and the preparation of the antimony silver telluride bulk material of high density, high purity, good repeatability, performance is better than commercial lead telluride sample. Compared with other preparation method of, the invention has the advantages of low reaction temperature, the experimental device is simple, the operation process is simple and controllable, and the like, wherein the temperature is lower than the solid phase reaction for about material melting point the 100-150 [...] , is far lower than the temperature of the use of traditional melting method (the 600-800 [...]), and is basically equivalent preparation period, greatly reduces the raw material sample the consumption of the electric power in the reaction process, reduce the cost to produce; the used hot-pressing process is simple and controllable, good repeatability, and according to the need to prepare different size and shape of the high-density bulk material.

Description of drawings

Figure 1 is XRD spectrum, chart of embodiment 1 after the first time in the solid phase reaction to obtain compound in the vertical short silver telluride antimony standard spectral diffraction peak position.

Figure 2 is XRD diagram of embodiment 1 in the secondary solid phase reaction to obtain compound spectrum.

Figure 3 is XRD diagram of embodiment 1 of the novel thermoelectric material spectrum body stibium of cytokines.

Figure 4 is the thermoelectric performance diagram of embodiment 1 of the novel thermoelectric material body stibium of cytokines.

Mode of execution

In order to better understand the invention, with further clarify the embodiment of the content of this invention, but the invention is not only limited to the following embodiment.

The following embodiment, elemental silver of greater than or equal to the quality purity 99.95% ; simple substance tellurium quality purity is greater than or equal to 99.9% ; purity elemental antimony quality of greater than or equal to 99.9% ; elemental silver, are tellurium and stibium powder, particle size is preferably 200 mesh the following.

Embodiment 1

Low temperature solid phase reaction process for preparing the hot pressing method of silver telluride antimony thermoelectric material, comprising the following steps:

1) proportioning: in accordance with the chemical formula AgSbTe_2.02 (in other words x to 0.02, Te surfeits 1%)of each element in the stoichiometric ratio is 1:1: 2.02 weighing powdered elemental silver, productivity is used as a raw material, the amount of raw materials 4.5g, wherein the elemental silver, the granularity of the tellurium and stibium are 325 mesh, 200 mesh, 200 mesh;

2) block sealing: the step 1) in the raw material is put into the agate mortar, full grinding 30 min, then the is pressed into tablet press with a diameter of 15 mm, the height of 4 mm of the cylindrical block, the resulting bulk density of about the density of silver antimony telluride 89% ; the diameter of the resulting block is 20 mm, length 12 cm quartz tube, in the vacuum 10^-3 Pa sealing under the conditions;

3) solid phase reaction for the first time: the step 2) of the vacuum after sealing the quartz tube is placed within a muffle furnace, at a rate of 100 the the [...] /h the 300 [...] , then at a rate of 30 the temperature slowly [...] /h to the 400 [...] , thermal insulation 8h, antimony compound shall be near-single-phase silver telluride[...] ;

4) secondary solid phase reaction: step 3) after grinding the crushing [...] , repeat steps 2) and 3) a time, in order to eliminate step 3) solid phase for the first time a small amount of impurities in the reaction product, [...] shall be single-phase silver telluride antimony compounds;

5) hot-pressing: the step 4) after grinding the crushing [...] , the diameter of the is 20 mm in the graphite die, hot-pressing sintering, hot-pressing temperature is 460 the [...] , time is 30 min, the pressure 35 MPa, reinforced to obtain the high-density of cytokines body stibium thermoelectric material, is superior to the relative density of 98.5%.

Step 3) to the first solid phase reaction, XRD pattern of the resultant product, as shown in Figure 1, a small amount of low-strength mixed peak exist, the resulting product is near single-phase silver telluride antimony thermoelectric compound; step 4) for the secondary solid-phase reaction, XRD pattern of the resultant product, as shown in Figure 2, its product is a single-phase silver telluride antimony compound, not see mixed peak.

Figure 3 is XRD chart of step 5) block spectrum obtained after the hot pressing, is a single-phase silver telluride antimony compound.

The high-density obtained by the embodiment of novel thermoelectric body stibium telluride thermoelectric properties of the material Figure 4, ZT value used for characterization, in the 300 can achieve near [...] 1.10. It is worth noting that, in preparing the embodiment 100-350 the ZT value [...] temperature range is greater than 0.7, this such that the sample in the process of practical application with a relatively high average ZT value and the thermoelectric conversion efficiency.

Embodiment 2

Low temperature solid phase reaction process for preparing the hot pressing method of silver telluride antimony thermoelectric material, comprising the following steps:

1) proportioning: in accordance with the chemical formula AgSbTe₂ (x is, 0) of the each element in the stoichiometric ratio of 1:1:2 weighing powdered elemental silver, productivity is used as a raw material, to the quality of raw materials in 4.35g;

2) block sealing: the step 1) in the raw material is put into the agate mortar, full grinding 60 min, then is pressed into the tablet press machine with a diameter of 15 mm, the height of 4 mm of the cylindrical block, the resulting bulk density of about the density of silver antimony telluride 86% ; the diameter of the resulting block is 20 mm, length 12 cm quartz tube, in the vacuum 10^-3 Pa sealing under the conditions;

3) solid phase reaction: of the step 2) of the vacuum after sealing the quartz tube is placed within a muffle furnace, at a rate of 80 the the [...] /h the 400 [...] , then at a rate of 25 the/ [...] h slowly raising the temperature to 450 the [...] , thermal insulation 12h, antimony compound shall be near-single-phase silver telluride[...] ;

4) hot pressing: the step 4) after grinding the crushing [...] , the diameter of the is 20 mm in the graphite die, hot-pressing sintering, hot-pressing temperature is 450 the [...] , time is 15 min, pressure 30 MPa, reinforced to obtain the high-density of cytokines body stibium thermoelectric material, is superior to the relative density of 98%.

The embodiment of novel telluride high-density of thermoelectric material body stibium ZT value of the thermoelectric properties of the 300 can achieve near [...] 0.87.

Embodiment 3

Low temperature solid phase reaction process for preparing the hot pressing method of silver telluride antimony thermoelectric material, comprising the following steps:

1) proportioning: in accordance with the chemical formula AgSbTe_2.02 (in other words x to 0.02) of the each element in the stoichiometric ratio of 1:1: 2.02 weighing powdered elemental silver, productivity is used as a raw material, the raw material quality 4.55g;

2) block sealing: the step 1) in the raw material is put into the agate mortar, full grinding 30 min, then the is pressed into tablet press with a diameter of 15 mm, the height of 4 mm of the cylindrical block, the resulting bulk density of about the density of silver antimony telluride 90% ; the diameter of the resulting block is 20 mm, length 12 cm quartz tube, in the vacuum 10^-3 Pa sealing under the conditions;

3) solid phase reaction for the first time: the step 2) of the vacuum after sealing the quartz tube is placed within a muffle furnace, at a rate of 50 the [...] /h raising the temperature to 350 the [...] , then at a rate of 20 the temperature slowly [...] /h to the 400 [...] , thermal insulation 10h, antimony compound shall be near-single-phase silver telluride[...] ;

4) secondary solid phase reaction: step 3) after grinding the crushing [...] , repeat steps 2) and 3) a time, in order to eliminate step 3) solid phase for the first time a small amount of impurities in the reaction product, [...] shall be single-phase silver telluride antimony compounds;

5) hot-pressing: the step 4) after grinding the crushing [...] , the diameter of the is 20 mm in the graphite die, hot-pressing sintering, hot-pressing temperature is 480 the [...] , time is 10 min, pressure 50 MPa, reinforced to obtain the high-density of cytokines body stibium thermoelectric material, is superior to the relative density of 98.5%.

The embodiment of novel telluride high-density of thermoelectric material body stibium ZT value of the thermoelectric properties of the 300 can achieve near [...] 1.02.

The stated above is the preferred embodiment of the invention, it should be noted that, for the ordinary technicians in this field are concerned, without departing from the invention to create the premise of design, can also be made a number of improvements and conversion, these all belong to the scope of protection of this invention.