Thermoelectric properties of p-type half-Heusler alloys Zr1-xTixCoSnySb1-y (0.0<x<0.5; y=0.15 and 0.3)

Half-Heusler alloys Zr1-xTixCoSnySb1-y (0.0 < x < 0.5; y = 0.15 and 0.3) are investigated for their possible use as high temperature thermoelectric materials. In these p-type materials, the Zr site is primarily substituted with Ti to reduce thermal conductivity (kappa), while the Sn content is varied to optimize thermoelectric properties. For these compositions, these alloys exhibit moderate resistivity (rho) in the m Omega cm range and high positive thermopower (kappa), on the order of hundreds of mu V/K. Measured Hall coefficients suggest that holes are dominant charge carriers. Calculated carrier mobilities are rather low in the range of 0.8-1.5 cm(2)/V s. Thermal conductivity (kappa) values as low as similar to 8.5-4.5 W m(-1) K-1 are also measured. The calculated thermoelectric figure of merit ZT = alpha T-2/rho kappa is as high as 0.2 at T = 1000 K, implying that these alloys could be potential p-type thermoelectric materials for energy conversion at high temperatures. (C) 2008 American Institute of Physics.