title: Metal-like electrical conductivity in LaxSr2-xTiMoO6oxides for high temperature thermoelectric power generation.
abstract: Increasing electrical conductivity in oxides, which are inherently insulators, can be a potential route in developing oxide-based thermoelectric power generators with higher energy conversion efficiency. In the present work, environmentally friendly non-toxic double perovskite LaxSr2-xTiMoO6(LSTM) ceramics were synthesized using a solid-state reaction route by optimizing the sintering temperature and atmosphere for high temperature thermoelectric applications. Rietveld refinement of XRD data confirmed a single-phase solid solution with a cubic structure in these double perovskites with the space-group Pm3[combining macron]m. SEM studies showed a highly dense microstructure in these ceramics. High electrical conductivity on the order of 105S m-1and large carrier concentration (∼1022cm-3) were obtained in these materials. The temperature-dependent electrical conductivity measurement showed that the LSTM ceramics exhibit a semiconductor to metal transition. Thermopower (S) measurements demonstrated the conductivity switching from a p-type to n-type behavior at higher temperature. A temperature dependent Seebeck coefficient was further explained using a model for coexistence of both types of charge carriers in these oxides. A conductivity mechanism of these double perovskites was found to be governed by a small polaron hopping model.
authors.affiliation: Plasmonics and Perovskites Laboratory, Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, UP 208016, India. tmaiti@iitk.ac.in.
authors.forename: Mandvi
authors.initials: M
authors.lastname: Saxena
authors.forename: Tanmoy
authors.initials: T
authors.lastname: Maiti