Tuning the Thermoelectric Transport Properties of Pseudo-Binary Cu2Te - Sb2Te3 System by Unidirectionally Solidification and Brine Quenching

Abstract

The rapidly depleting available energy resources have led to an increased research focus on the development of alternative energy sources. In this aspect, research on the development of efficient thermoelectric (TE) materials and integrating them into devices has taken a lead role in recent years worldwide. Thermoelectricity is a phenomenon of conversion of thermal energy into electrical energy and vice versa. The conversion efficiency of a TE material is dependent on a dimensionless parameter known as the figure of merit zT, which is directly related to the product of electrical conductivity (σ) and the square of the Seebeck coefficient (S) whereas inversely related to the thermal conductivity (κ). This research contains two studies. In the first studies, we explore in-situ lamellar composites of (Cu2Te) 62.02-(Sb2Te3)37.98 produced by directional solidification using a modified Bridgman apparatus and its effect on the thermoelectric properties. The eutectic microstructure under higher growth rates exhibits a cellular microstructure due to growth instability (and hence segregation at cell boundaries) with cell spacing varying with growth rates. Further, a quantitative evaluation of the scale of the microstructure in terms of interlamellar spacings allows us to evaluate the role of the microstructure in tuning the thermoelectric properties as a function of temperature. An additional significant observation of the present work is a relatively mild variation of the power factor across a range of temperatures (300 K to 600 K) in this eutectic system along the transverse direction. In the second study, we report the microstructure and thermoelectric Properties Of (Cu2Te)X(Sb2Te3)100-x pseudobinary system synthesized by brine quenching method and compare the microstructure and transport properties to the same composition synthesized by solid-state synthesis.