Investigation of Compositional Microstructural and Phase Characteristics on the Performance of Environmentally Friendly Oxide based Materials for Mid Temperature Thermoelectric Application

Abstract

The study of thermoelectric is one of the hottest topic for research due to the commendatory benefits it brings to mankind. Thermoelectric materials are primarily used for the conversion of waste heat to electricity. Various classes of materials like chalcogenides, skutterudites, clathrates, half-Heusler alloys, polymers, and oxides have been explored as thermoelectric out of which oxide-based materials have shown higher tolerance to heat and better conversion efficiency. Thus, this study is focused on material structures such as BiFeO3 (Perovskites), NiMoO4 (Molybdates), and MBi2O4 (Kusachiites) and the elucidation of their properties. Here, I have probed various strategies such as doping of thermally stable element, and addition of impurities as secondary phases, changes in both compositions, and microstructures, to study their influence on the thermoelectric properties of above materials. The dopant La successfully increases the stability of the material over the temperature. However, the BiFeO3 possess the high electrical conductivity it leads to high zT than La doped BiFeO3 . The benefit of La doping arise by increasing the stability. In the place of M site we substituted Ni, Cu, and Zn in MBi2O4 . Among these, Ni possess high zT due to the presence of Ni3+ and surface porous of this material which is about 10 times higher than the CuBi2O4 . Cu disturbed the BiFeO3 due to the formation of CuBi2O4 along with the secondary phases of BiFeO3 . The Cu disturbed lattice possess the less electrical conductivity while the Seebeck coefficient increased by energy filtering effect. The stability increases in Cu disturbed BiFeO3 even BiFeO3 posses high zT than Cu disturbed BiFeO3 . Finally, the molybdates thermoelectric properties examined by varying the synthesis process. According to the modification in synthesis process one material formed with nanorod structure while other in nanosphere like structure. The nanorod morphology possess high electrical conductivity but low Seebeck coefficient, and high thermal conduct