Understanding the Anomalously Low Thermal Properties of Zr3ni3-Xcoxsb4 Thermoelectric Material

Abstract

By controlling the SPS temperature, we prepared Zintl Zr3Ni2.9Co0.1Sb4 samples, namely Co doping in Ni sites of Zr3Ni3Sb4, and investigated the corresponding thermoelectric properties. It was found that a significant reduction of the lattice thermal conductivity occurred due to Co doping while tuning the SPS temperature slightly affected ZT values. The influence of aliovalent element Co doping on the phonon structure and transport properties of Zr3Ni3Sb4 was conducted through first-principles calculations. Co doping increased phonon anharmonicity, induced the collapse of the splitting between longitudinal-optical phonon and transverse-optical phonon, narrowed the phonon bandgaps, and avoided the crossing between acoustic and optical phonons, resulting in suppressed phonon velocity and lifetime, leading to a remarkable reduction in lattice thermal conductivity. Our finding enriches the understanding of aliovalent doping in thermal transport theories which should be applicable to other thermoelectric systems.

Keywords: Thermoelectric materials, Aliovalent doping, Zr3Ni3Sb4, Phonon transport properties, Thermal conductivity.