Microstructural effects on the thermoelectric performance of Ge_0.962Bi_0.038Te_1.057

Thermoelectrics is a renewable energy method, capable of a direct conversion of waste heat into useful electricity, which can be applied for tackling global warming, high pollution levels and dilution of fossil energy sources. For this purpose novel and highly efficient thermoelectric compositions should be developed and analyzed under practical operation conditions. In the current research the effects of grain size and thermal treatment under operation conditions on the thermoelectric performance of Ge_0.962Bi_0.038Te_1.057 were investigated. Following hot-pressing both positive electronic and lattice effects were identified for sub-micron grained samples, enabling very high figure of merit, ZT, values of up to 1.8. These values were slightly degraded down to ≈ 1.4 following thermal treatment, mainly due to grain coarsening, highlighting the requirement of grain growth inhibition for maximizing the potential of this composition.