Anisotropic layered Bi2 Te3 -In2 Te3 composites: Control of interface density for tuning of thermoelectric properties

Abstract

Layered (Bi1-xInx) 2 Te3 -In2 Te3 (x = 0.075) composites of pronounced anisotropy in structure and thermoelectric properties were produced by zone melting and subsequent coherent precipitation of In2 Te3 from a (Bi1-xInx) 2 Te3 (x > 0.075) matrix. Employing solid state phase transformation, the Bi2 Te3 /In2 Te3 interface density was tuned by modifying the driving force for In2 Te3 precipitation. The structure-property relationship in this strongly anisotropic material is characterized thoroughly and systematically for the first time. Unexpectedly, with increasing Bi2 Te3 /In2 Te3 interface density, an increase in electrical conductivity and a decrease in the absolute Seebeck coefficient were found. This is likely to be due to electron accumulation layers at the Bi2 Te3 /In2 Te3 interfaces and the interplay of bipolar transport in Bi2 Te3. Significantly improved thermoelectric properties of Bi2 Te3 -In2 Te3 composites as compared to the single phase (Bi1-xInx) 2 Te3 solid solution are obtained.