Graphite sintered strontium praseodymium titanate perovskite for thermoelectric applications

Here Pr³⁺ was introduced in the Sr²⁺ site in Sr_1-x Pr_xTiO₃ (x = 0.05, 0.075, 0.10, 0.125, 0.15, 0.20) system followed by two step graphite burial sintering. Powder reduction helps to increase the carrier concentration and the doped sample pellet reduction minimizes Double Schottky Barrier generated by strontium and oxygen vacancies at grain boundary by regulating the point defects. Samples with x ≥ 0.10 shows splitting and asymmetry of (200) and (310) peak in XRD indicating structural transformation from cubic to tetragonal phase. XPS spectra of the samples confirmed the formation of oxygen vacancies and reduction of Ti⁴⁺ to Ti³⁺ induced by graphite burial sintering resulting in enhanced carrier concentration. A maximum power factor of 1.8 mW/mK² was obtained for Sr_0.9 Pr_0.1TiO₃ samples at 673 K. Reduced thermal conductivity due to porous structure, Pr defect centers, oxygen vacancy clusters together with enhanced power factor lead to a maximum figure of merit 0.33, making this an ideal candidate as n type legs in thermoelectric generators.