Synthesis Of P-type Mg-Si Based Thermoelectric Material And Its Properties

This paper have reviewed detailed the thermoelectricity, the history of thermoelectric materials and the current situation of Mg2Si based thermoelectric material. The studies in existence showed that the solid solutions which based with Mg2Si and doped with other elements are good thermoelectric semiconductors working at mid-temperature (400-700K).The basic thermodynamic theory was introduced to calculate the Gibbs function changes of Mg-Si-0 system and was used to discuss the process of synthesizing the Mg2Si powder. The probability of synthesizing the Mg2Si powder by solid-state reaction at low temperature and the techniques were confirmed. The result showed that the Mg2Si powder could be synthesized by solid-state reaction at low temperature but in the system the impurity of MgO appeared easily. It is because of that the element of Mg is very active and it would react with the rudimental O2 in the container and at the same time the Mg2Si could be oxide when the temperature descending. The techniques of solid-state reaction must be mended because the MgO is one of the impurities that could deduce the thermoelectric properties.Ag was selected for dopant in Mg2Si synthesizing process. The influence of dopants amount on thermoelectric properties of Mg2Si specimen was researched. The p-type Mg2Si based thermoelectric materials was synthesized first time by solid-state reaction. The result showed that when the dopants amount is increasing, the Seebeck coefficient and the electrical conductivity of samples are increasing too, but the thermal conductivity has not an obvious change. Z and ZT of specimen doped with 15000ppm Ag are the largest, and the values are 18.2 X 10-6 K-1 and 0.01 respectively.The nono-powder of BN was selected to change the thermoelectric properties of Mg2Si based thermoelectric materials. The result shows thatwhen the powder of BN was doped in the Mg2Si based thermoelectric materials, the thermal conductivity of sample is decrease obviously, and the electrical conductivity is decreasing at the same time. The doping with a little BN powder is favorableness for the Mg2Si based thermoelectric materials' thermoelectric properties.