Simultaneous enhancement of Seebeck coefficient and electrical conductivity in ZnSnO by the engineering of grain boundaries using post annealing

Abstract

In this manuscript, we have reported the simultaneous enhancement in Seebeck coefficient and electrical conductivity by controlling the density and size of the grains. The grain boundaries are acting as barriers for the low energy carriers at the grain boundaries, which resulted in the enhancement of mobility of carriers. The high mobility of carriers simultaneously enhances the Seebeck coefficient and conductivity of the material under investigation. This argument was tested by deliberately engineering the grain boundaries in bulk Zinc Tin Oxide (ZnSnO) by the post thermal annealing method. The ZnSnO pallets were prepared by mixing of ZnO and Sn metal powders (24:1) by hydraulic press at very high pressure. SEM images demonstrated that the grain boundaries were found to be increased with increase in annealing temperature. It was observed that the values of Seebeck coefficient and power factor were increased to maximum (120 μV/°C and 4.8×10−4 W m−1 K−2 respectively) at maximum annealing temperature. While the supplementary measurements like XRD and Raman spectroscopy were used to support this argument.