Effect Of Sintering On The Performance Of N Type Pseudp-ternary Thermoelectric Materials

Thermoelectric material is a kind of functional material which can be transformed into each other electrical and thermal energy. Found that the Seebeck effect and Pletier effect is widely used to provide post of thermoelectric materials and solid theoretical foundation. Thermoelectric materials generally have the advantages of small volume,light, no pollution and the advantages of recycling and easy to control. However,manufacturing device is composed of thermoelectric materials(such as refrigerators etc.)which its efficiency is far behind the traditional process. The thermoelectric figure of merit Z is used usually to judge the efficiency of thermoelectric materials. The higher the Z indicates the material thermoelectric efficiency is higher. Therefore, how to improve the Z becomes a core problem in the research field of thermoelectric materials.Bi2Te3 thermoelectric material is one of the most popular materials in the current field of thermoelectric materials research. Because of its good thermoelectric properties, it has been widely used in the production of semiconductor components. In this paper,based on the n-type pseudo-ternary Bi2Te3 based thermoelectric materials, n-type Bi2Te3 solid solution alloy is prepared by elemental melting combination method. The n-type carbon fiber doped Bi2Te3 composite powder is obtained by doping the carbon fiber.Under inert gas environment, the thermal conductivity, the Sebek coefficient and the carrier mobility measurement and calculation of Z of the n-type carbon fiber doped Bi2Te3 composite block are analyzed in different sintering temperature.The microstructure test results shows that by SEM and XRD the carbon fiber distribution is uniform in the n-type pseudo-ternary Bi2Te3 based thermoelectric materials and played a more significant role in connection. Due to the high temperature sintering, the structure of the n-type pseudo-ternary Bi2Te3 based thermoelectric materials becomes more compact. So the original grain structure can be dispersed together and become larger grains. The overall structure changes loosely irregularly shape into apparent terrace-like structure which enhances the thermoelectric properties of the material and is significance to upgrade the Z. The carriers’ transport analysisshows that the mobility and concentration of the carriers increase with sintering temperature rises in a certain temperature range. Based on the results of thermoelectric performance, the thermal conductivity κ of the n-type carbon fiber doped Bi2Te3 composite decreased firstly and then increased with the increase of the sintering temperature under hot pressing temperature constant. And reached about 300 ℃ in the sintering temperature reaches a maximum value. The conductivity σ is first decreased and then increased trend, and reached 250 ℃ in the sintering temperature reaches a minimum value. The Seebeck coefficient α of the composite material first increased and then decreased, when it reached 300℃ in the sintering temperature reaches a maximum value. The carrier mobility of mob showed increased with temperature rising trend;Thermoelectric Z showed an increasing trend, and reached the maximum at 300 ℃which also proved that the optimal sintering temperature of 300 ℃ for low temperature zone of the experimental materials.In summary, using SEM, XRD and high temperature sintering, by the analysis of the microstructure, the carriers’ transport and the thermoelectric properties, the relationship of the performance of the n-type pseudo-ternary carbon fiber doped Bi2Te3 based composite thermoelectric materials with sintering temperature are obtained. The optimal sintering temperature is gotten. The impact mechanism of sintering temperature on the thermoelectric performance is revealed. The results have important significance for the further study of the performance of pseudo-ternary thermoelectric materials.