Reduced thermal conductivity of Bi-In-Te thermoelectric alloys in a eutectic lamellar structure

Directional solidification of Bi2Te3-In2Te3 eutectic alloys allows for exploiting both crystal anisotropy and internal interface density for the enhancement of thermoelectric properties. A lamellar structure with a spacing of 2 μm was produced for the eutectic alloy Bi-16.5In-60Te (at%). Coherent Bi2Te3-In2Te3 interfaces sharing the same Te atomic layer were found. The Bi2Te3-In2Te3 composites are n-type thermoelectric materials with lower thermal conductivity than each of the constituent phases. The eutectic alloy with a higher interface density exhibits a lower phonon thermal conductivity than off-eutectic alloys. The disparity between experimentally determined values and calculations using composite models concerning the thermoelectric properties demonstrates the enhanced potential of internal interfaces for improving thermoelectric properties.