TiNiSn: A gateway to the (1,1,1) intermetallic compounds

Recent awareness of the transport properties of Skutterudite pnictides has stimulated an interest in numerous other intermetallic compounds having a gap in the density of states at the Fermi level including the MNiSn compounds where M = (Ti, Zr, Hf). These intermetallic half-Heusler compounds are characterized by high Seebeck coefficients ({minus}150 to {minus}300 {micro}V/deg.) and reasonable carrier mobilities (30 to 50 cm{sup 2}/V-s) at room temperature which make them attractive candidates for intermediate temperature thermoelectric applications. Samples of TiNiSn were prepared by arc melting and homogenized by heat treatment. The temperature dependence of the electrical resistivity, Seebeck coefficient, and thermal diffusivity of these samples was characterized between 22 C and 900 C. The electrical resistivity and thermopower both decrease with temperature although the resistivity decreases at a faster rate. Electrical power factors in excess of 25 {micro}W/cm-C{sup 2} were observed in nearly single phase alloys within a 300 to 600 C temperature range. A brief survey of other selected ternary intermetallic compounds is also presented