Thermoelectric properties and thermal expansion of quaternary layered compound SrFZnSb

Layered semiconductors have received increased attention recently due to the potential as high-performance thermoelectric materials. The quaternary layered compound SrFZnSb adopts ZrSiCuAs-type structure with insulating [Sr2F2]2+ layers and conductive [Zn2Sb2]2+ layers alternately stacked along the c-axis. As a narrow band-gap p-type semiconductor, SrFZnSb has a higher electrical conductivity and smaller Seebeck coefficient in comparison with isostructural thermoelectric compound BiOCuSe. Thermal properties measurements for pristine SrFZnSb reveal that its total thermal conductivity drops to 1.33 W m−1 K−1 at 773 K with the lattice thermal conductivity fitting the law of T−1. The maximum thermoelectric figure of merit ZT for SrFZnSb reaches 0.17 at 773 K. In addition, SrFZnSb presents the bulk thermal expansion coefficient of 1.2–1.5 × 10−5 K−1 within the temperature range of 300–700 K, smaller than 6.74 × 10−5 K−1 for BiOCuSe.