Sodium doped polycrystalline SnSe: High pressure synthesis and thermoelectric properties

Abstract p -type Na x Sn 1- x Se bulks were prepared by combining high pressure synthesis and spark plasma sintering. The final samples were characterized with XRD and SEM, and demonstrated strong structural anisotropy with the b-c planes in the grains preferentially orientated perpendicular to the SPS compressing direction. High pressure prompted Na doping process and increased the hole concentration up to 3.08 × 10 19  cm −3 in Na 0.02 Sn 0.98 Se, leading to significant increased electrical conductivity and power factor. Meanwhile, the thermal conductivity was substantially suppressed after Na doping. The highest ZT of 0.87 was achieved in the optimal Na 0.02 Sn 0.98 Se at 798 K measured along the direction perpendicular to the SPS compressing.