Layered PrZnOX (X = P, As) compounds: Promising n-type thermoelectric materials with low lattice thermal conductivity

The heteronanionic materials exhibit low lattice thermal conductivities and excellent electronic transport properties on account of their unique ZrSiCuAs-type crystal structures. In this study, the thermoelectric (TE) properties of the layered PrZnOX (X = P, As) compounds are theoretically elaborated in combination with the first-principles calculations and Boltzmann transport theory. The layered PrZnOP and PrZnOAs compounds are direct semiconductors with wide bandgaps of 1.96 eV and 1.88 eV within HSE06 hybrid functional, respectively. Through a comprehensive evaluation of the crystal structures and mechanical properties, the PrZnOX (X = P, As) compounds are thermodynamically and mechanically stable. The lattice thermal conductivities are 3.60 W/mK and 3.26 W/mK for the PrZnOP and PrZnOAs compounds at 300 K, respectively. The n-type layered PrZnOX (X = P, As) compounds exhibit large power factors on account of the high electrical conductivities and large Seebeck coefficients compared to the p-type situations. Consequently, the high figure of merits (ZTs) of 1.88 and 1.78 at 1000 K are discovered for the n-type PrZnOX (X = P, As) compounds. Our current work not only reveals the underlying mechanisms responsible for the excellent TE properties of PrZnOX (X = P, As) materials, but also elaborates the potential TE application of heteroanionic material at high temperature.