Solid Solution Behavior and Thermoelectric Properties of Half-Heusler (Zr_x, Nb_1−x)(Ni_y, Co_1−y)Sn Alloy

Abstract

  ZrNiSn and NbCoSn are half-Heusler compounds which have excellent n-type thermoelectric properties. In the present study, solid solution behavior of quaternary half-Heusler Nb(Co, Ni_x)_1+xSn (x=0, 0.05, 0.10, 0.15) and quinary half-Heusler (Zr_x, Nb_1−x)(Ni_y, Co_1−y)Sn (x, y=0.25, 0.50, 0.75) alloys has been investigated aiming at the reduction of lattice thermal conductivity of alloys due to the solid solution effect. In the quaternary alloys, it was revealed that Ni atoms tend to substitute for the Co-sites instead of occupying the vacancy-sites of half-Heusler NbCoSn. In the quinary (Zr_x, Nb_1−x)(Ni_y, Co_1−y)Sn alloys, it is suggested that half-Heusler solid solution phase seems to be formed. As a result, the thermal conductivity of sintered (Zr_0.5, Nb_0.5)(Ni_0.5, Co_0.5)Sn alloys is reduced by about 40 and 60% from that of ZrNiSn and NbCoSn alloys, respectively.