Abstract
Present work investigates the effect of calcium doping on the structure and thermoelectric properties of Sr2TiCoO6 (STC) double perovskite. Environmentally friendly rare earth free CaxSr2−xTiCoO6 (0.0 ≤ x ≤ 0.3) (CSTC) ceramics were synthesized using solid state synthesis route. CSTC ceramics were found to possess a cubic crystal structure with Pm3¯m space group as confirmed by Rietveld refinement of XRD data. Microstructure analysis was carried out by SEM and energy dispersive x-ray spectroscopy. The temperature dependent electrical conductivity and thermopower of these oxides showed the semiconductor to metal transition at around 700 K. X-ray photoelectron spectroscopy (XPS) confirmed the presence of multiples oxidation states of Co and Ti creating defect sites in these oxides. CSTC ceramic samples exhibited positive Seebeck coefficient implying p-type behavior. Charge transport mechanism of all the CSTC samples was found to be governed by small polaron hopping model.
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