Studies on strontium substituted rare earth manganites

Sintering, electrical conductivity and thermal expansion behaviour of combustion synthesised strontium substituted rare earth manganites with the general formula Ln_1−xSr_xMnO₃ (Ln=Pr, Nd and Sm; x=0, 0.16 and 0.25) have been investigated as solid oxide fuel cell cathode materials. The combustion derived rare earth manganites have surface area in the range of 13–40 m²/g. Strontium substitution increases the electrical conductivity values in all the rare earth manganites. With the decreasing ionic radii of rare earth ions, the conductivity value decreases. Among the rare earth manganites studied, (Pr/Nd)_0.75Sr_0.25MnO₃ show high electrical conductivity (>100 S/cm). The thermal expansion coefficients of Pr_0.75Sr_0.25MnO₃ and Nd_0.75Sr_0.25MnO₃ were found to be 10.2×10⁻⁶ and 10.7×10⁻⁶ K⁻¹ respectively, which is very close to that of the electrolyte (YSZ) used in solid oxide fuel cells.