Based On Resonance State Theory For GeTe And SnTe Thermoelectric Materials By First Principle Calculation

Thermoelectric materials, which have no pollution and mechanical wear, can directly transform thermal energy into electrical energy, offering opportunities to harvest useful electricity from waste heat in automobiles, industrial plants, and other energy intensive processes. Middle temperature thermoelectric materials such as germanium telluride(GeTe), tin telluride(SnTe) were received extensive attention for the potential application of recovery power generation from waste heat. The concentration of Ge vacancies in GeTe directly determined the concentration of carries, which was significant for thermoelectric properties of materials. SnTe was a narrow band gap semiconductor material free IV-VI, in which a resonace level introduced by doping through resonance state theory, an improved thermoelectric properties was expected.In this investigation, the band structure and effect of vacancies of GeTe and SnTe were calculated by using the first principle density functional theory with the generalized gradient. In order to verify the result of above calculation, Aluminum was doped into SnTe..It was studied that the effects of different concentrations of Ge vacancy on the electronic structure and transport properties of GeTe materials. The main conclusions were as follows: the concentration of Ge vacancies was analysed by employing the energy band diagram. It was observed that the density of states near the Fermi level curve slope increasing with the increasing of Ge vacancies concentration. Based on Mott formula, the Seebeck coefficient was dramatically increased, which was beneficial to improve the thermoelectric figure of merit value of materials.By doping the third main group elements into Sn site in SnTe, the investigation of resonance phenomenon was conducted. The resonace phenomenon only appeared while Al and In were doped, and the optimum effect was observed by doping of Al. Also experiment was conducted to verify the above calculation result. The Al:SnTe materials were prepared by utilizing two methods, namely high-energy ball milling and high temperature melting method. By analysing of Seebeck coefficient and ZT value as a function of temperature, it was found out that the properties of thermoelectric properties were improved, which correspond to the results of calculation.