Strong quartic anharmonicity and thermoelectric performance in antiperovskite Sr3XN (X = P, As, Sb, and Bi)

Antiperovskite (APV) materials have garnered significant attention due to their diverse physical properties. The self-consistent phonon (SCP) theory and the Boltzmann transport equation (BTE) were combined to calculate thermal and electronic transport properties of APV Sr3XN (X = P, As, Sb, Bi) based on density functional theory (DFT). Pronounced quartic anharmonicity was identified in Sr3PN and Sr3AsN, attributed to the vibrations of Sr atoms. This distinctive characteristic induces four-phonon (4ph) scattering, significantly reducing the lattice thermal conductivity (κL), particularly at elevated temperatures such as 900 K, with values as low as 0.58 W·m−1·K−1 for Sr3PN. Additionally, Sr3BiN exhibits remarkable electrical conductivity and a high Seebeck coefficient, leading to a promising figure of merit (ZT) of up to 1.03, underscoring its potential as a thermoelectric material. These findings demonstrate that the ultra-low lattice thermal conductivity driven by 4ph scattering, coupled with excellent thermoelectric properties, makes these materials promising candidates for high-efficiency thermoelectric applications.