Thermoelectric Properties of Ti x (Hf y Zr1−y )1−x NiSn0.998Sb0.002 Half-Heusler Ribbons

Abstract

Ribbons of Ti x (Hf y Zr1−y )1−x NiSn1−z Sb z (x = 0.1 to 1, y = 0.1 to 0.9, z = 0, 0.002, 0.004) were prepared by spin casting and annealed for 1 h at T a = 1000 K, 1050 K, 1073 K, and 1100 K. The crystal phase of the ribbons was investigated by x-ray diffraction analysis and transmission electron microscopy. All the ribbons consisted of a phase with a half-Heusler structure. The Seebeck coefficient, electrical conductivity, thermal conductivity, power factor, and figure of merit ZT at room temperature were clarified experimentally as a function of x, y, z, and T a. Despite the large thermal conductivity, the power factor and figure of merit were remarkably large at x = 0.5, y = 0.5, z = 0.002, and T a = 1073 K, because the Seebeck coefficient and electrical conductivity were large.