Strong anharmonicity and medium-temperature thermoelectric efficiency in antiperovskite Ca3XN (X = P, As, Sb, Bi) compounds

Abstract

In this work, we employ density functional theory (DFT) calculations to systematically investigate the thermal and electronic transport properties as well as the thermoelectric performance of antiperovskite (APV) compounds within the Ca₃XN family, where X = P, As, Sb, and Bi. Here, post calculations are performed based on self-consistent phonon (SCP) theory and the Boltzmann transport equation (BTE), specifically accounting for four-phonon scattering processes. Interestingly, these materials display notably low lattice thermal conductivity (κ_L), approximately 1.1 W m⁻¹ K⁻¹ at 900 K. As a result, both Ca₃AsN and Ca₃SbN exhibit remarkably high figure of merit (ZT) values at elevated temperatures (300–900 K), exceeding 1.1. Moreover, the selected APV materials, especially Ca₃AsN, Ca₃SbN, and Ca₃BiN, maintain promising thermoelectric properties also in the medium-temperature range (≈600 K), with ZT values of approximately 0.8, along with unconventional temperature-dependent thermal conductivities. Our work serves as a proof-of-concept example for designing materials for future medium-/high-temperature thermoelectric applications.