Anisotropic layered Bi(2)Te(3)-In(2)Te(3) composites: control of interface density for tuning of thermoelectric properties

Layered (Bi(1−x)In(x))(2)Te(3)-In(2)Te(3) (x = 0.075) composites of pronounced anisotropy in structure and thermoelectric properties were produced by zone melting and subsequent coherent precipitation of In(2)Te(3) from a (Bi(1−x)In(x))(2)Te(3) (x > 0.075) matrix. Employing solid state phase transformation, the Bi(2)Te(3)/In(2)Te(3) interface density was tuned by modifying the driving force for In(2)Te(3) precipitation. The structure-property relationship in this strongly anisotropic material is characterized thoroughly and systematically for the first time. Unexpectedly, with increasing Bi(2)Te(3)/In(2)Te(3) 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 Bi(2)Te(3)/In(2)Te(3) interfaces and the interplay of bipolar transport in Bi(2)Te(3). Significantly improved thermoelectric properties of Bi(2)Te(3)-In(2)Te(3) composites as compared to the single phase (Bi(1−x)In(x))(2)Te(3) solid solution are obtained.