Mode Gruneisen parameters of an efficient thermoelectric half-Heusler

Half-Heusler compounds have recently been identified as promising thermoelectric materials, but their relatively high thermal conductivities impede the further improvement of thermoelectric performance. The knowledge of phonon vibrational properties provides a fundamental understanding of the thermal transport behavior of solids and thus could serve as a guidance on further suppressing the thermal conductivity. Herein, a highly efficient p-type half-Heusler thermoelectric alloy FeNb0.8Ti0.2Sb is taken as an example to explore its phonon vibrational properties. Phonon spectrum with the frequencies down to 10 cm(-1) and its evolution with pressure for the studied material are provided by Raman scattering. It is found that two vibrational modes with the frequency > 200 cm(-1) display a common mode frequency increase with increasing pressure. Based on the bulk modulus from synchrotron X-ray powder diffraction and phonon frequency shifts, the mode Gruneisen parameters are obtained. Our results establish characteristic phonon vibrational properties of this high-performance half-Heusler thermoelectric alloy. Published by AIP Publishing.