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

Abstract

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 (κ), while the Sn content is varied to optimize thermoelectric properties. For these compositions, these alloys exhibit moderate resistivity (ρ) in the mΩcm range and high positive thermopower (α), on the order of hundreds of μV∕K. Measured Hall coefficients suggest that holes are dominant charge carriers. Calculated carrier mobilities are rather low in the range of 0.8–1.5cm2∕Vs. Thermal conductivity (κ) values as low as ∼8.5–4.5Wm−1K−1 are also measured. The calculated thermoelectric figure of merit ZT=α2T∕ρκ is as high as 0.2 at T=1000K, implying that these alloys could be potential p-type thermoelectric materials for energy conversion at high temperatures.