Low lattice thermal conductivity induced by interlayer anharmonicity in p-type BaFZnAs compound with high thermoelectric performance

Inspired by the excellent thermoelectric (TE) performance of ZrSiCuAs-type materials, the crystal structure, thermal and electronic transport mechanisms, and TE properties of the BaFZnAs compound are explored using first-principles calculations and Boltzmann transport theory. The BaFZnAs compound is an anisotropic material, with a direct bandgap of 1.20 eV determined by the Heyd-Scuseria-Ernzerhof (HSE06) functional. The [Zn2As2]2- layer within BaFZnAs compound forms carrier transport channel, which is beneficial for high power factor. The strong out-of-plane interlayer anharmonicity of the [Ba2F2]2+ and [Zn2As2]2- layers with weak interactions leads to a low lattice thermal conductivity (1.64 W/mK at 300 K) for the BaFZnAs compound. Based on the carrier relaxation time evaluated within the consideration of multiple carrier scattering rates and electronic transport parameters, the optimal ZTs of 1.44 and 2.06 are achieved for n-type and p-type BaFZnAs compounds at 900 K, respectively, associating with the corresponding ZTs of 2.10 (0.72) and 2.64 (0.51) along the a-axis and c-axis directions. Our present work not only offers multifaceted insights into the thermal and electronic transport properties of BaFZnAs compound, but also provides a new inspiration for further TE exploration of ZrSiCuAs-type materials.