不同Type I - III相比例之BaGaGe晶籠合金之熱電特性研究

Abstract

In this study,the Ba-Ga-Ge thermoelectric alloys with vary ratios of Type I - III phases were prepared by arc melting and heat treatment.The effect of vary ratios of Type I - III phases on thermoelectric properties was studied. From the ICP-MS and metallographic analysis,the composition and phase ratio of Ba-Ga-Ge alloys were determined.The Ga content reduced gradually with the increase of Type III phase ratio.From BEI and XRD analysis,All the Ba-Ga-Ge alloys were composed of the Type I,Type III and Ge phase. On thermoelectric performance,the electrical conductivity decreases and Seebeck coefficient increases gradually with increasing temperature.The electrical conductivity and Seebeck coefficient do not change much in the Type III phase ratio between 28 and 59.But the clathrate compound structures are influenced by Ge phase content which is increased gradually with the increase of the Type III phase ratio.As a result,both the electrical conductivity and Seebeck coefficient decreased.The thermal conductivity decreased gradually with the increasing of Type III phase ratio.When the ratio of Type I - III phases is 68 - 32, the figure of merit is 1 at 500 ℃ optimally.