IMF2017

Thermoelectric materials are considered as cleanest source of energy generation by converting waste heat into electricity. Recently we investigated wide range of SrTiO₃ based double perovskites to evaluate their potential for high temperature thermoelectric applications. In this report, overview of A_xSr_2-xTiBO₆ (A = Ba, La and B= Fe, Co, Mo) based double-perovskites were presented to understand the role of crystal structure, microstructure, multiple oxidation states of constituent atoms in order to achieve better figure of merit (ZT) for thermoelectric power generation. The thermo-power (S), electrical conductivity (σ) and thermal conductivity (k) were measured in the temperature range 25 K-1273 K. Exceptionally high thermopower (~ 800 μV/K) was obtained in some compositions. On the other hand metal-like electrical conductivity (~105 S/m) was achieved in some of these double-perovskites. It was observed that these oxides invariably demonstrated semiconductor (dσ/dT > 0) to metal (dσ/dT < 0) transitions. Manipulating the dopants in A-site and B-site of these SrTiO₃­ based double-perovskites, both n-type and p-type behaviors were observed. Moreover some compositions exhibited temperature driven p-n type conduction switching along with colossal change in thermopower, which could be useful to develop next generation multifunctional electronic devices like switches, diodes, thermistors. Dielectric study confirmed that these double-perovskites exhibited relaxor ferroelectric like behavior. Moreover, it was shown that inducing dipolar glassy phase due to relaxor ferroelectricity could be an alternative way of designing thermoelectric materials similar to popular “phonon-glass electron-crystal” model.