二段熱処理による単相 β-Zn4Sb3 熱電材料の試作および添加元素の影響

Abstract

Single phase β-Zn4Sb3 was prepared by applying a two-stage heat treatment and the carrier concentration of β-Zn4Sb3 was controlled by doping with doping elements. The undoped and doped samples were prepared by direct melting followed by two-stage heat treatment at 723 and 673 K after solidification of the samples in sealed quartz ampoules. Impurity doping of the samples was performed by adding one atomic percent of Se, In, Pb, Te or Bi. The resulting samples were characterized by X-ray diffraction, differential thermal analysis (DTA), optical microscopy, electron probe micro-analysis (EPMA) and their Seebeck coefficients determined at room temperature. The undoped samples were shown by X-ray diffraction and DTA to comprise of single phase β-Zn4Sb3, while the doped samples contained multiple phases. From the measurements of the Seebeck coefficient, all samples were found to be of the p-type and all found to have almost the same values. These results indicate that β-Zn4Sb3 has limited solubility for these doping elements for controlling carrier concentration.