Thermoelectric performance of n-type polycrystalline SnSe with surface depletion by pressureless sintering

Abstract

In this study, polycrystalline SnSe samples were prepared by a series of mechanical alloying (MA), uniaxial compaction, and subsequently pressureless sintering. It was found that the grains in the resultant SnSe samples grow along the (1 1 1) plane direction, resulting in forming a layered structure. Depending on the sintering time, the SnSe samples show the conversion of p-type conduction with the Seebeck coefficient value of +503 mu V/K to n-type conduction with the Seebeck coefficient value of -1500 mu V/K. The samples were characterized using X-ray diffraction and Raman spectroscopy to reveal that the transition of the Seebeck properties is due to the imbalanced composition of SnSe caused by impurities (SnSe2, SnSe1-x) formed during pressureless sintering. Also, the experiments and characterization results demonstrated a possibility to enhance thermoelectric properties if the pressureless sintering conditions would be well-controlled.