Peculiarities of thermoelectric half-Heusler phase formation in Zr-Co-Sb ternary system

The phase equilibria in the Zr-Co-Sb ternary system were studied at 873 K by means of X-ray and metallographic analyses in the whole concentration range. The interaction between the elements results the formation of four ternary compounds at investigated temperature: ZrCoSb (MgAgAs-type), Zr6CoSb2 (K2UF6-type), Zr5CoSb3 (Hf5CuSn3-type) and Zr5Co0.5Sb2.5 (W5Si3-type). The limited composition Zr5CoSb3 of the solid solution based on the Zr5Sb3−4 binaries is considered as compound with Hf5CuSn3 structure type. The influence of the disordering and defects in the crystal structure of ZrCoSb on the physical properties was analyzed. The performed electronic structure calculations are in good agreement with electrical and magnetic studies.