Mode Grüneisen 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 FeNb 0.8Ti 0.2Sb 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 Grüneisen parameters are obtained. Our results establish characteristic phonon vibrational properties of this high-performance half-Heusler thermoelectric alloy. © 2018 Author(s).