Influence of Ca ²⁺ substitution on thermal, structural, and conductivity behavior of Bi _1-x Ca _x FeO _3-y (0.40 & x ; 0.55)

Bi _1-x Ca _x FeO _3-y (0.40 & x ; 0.55) perovskite oxides have been synthesized by solid-state reaction method to study their properties as a cathode material for intermediate temperature solid oxide fuel cells. The as prepared samples were characterized by X-ray diffraction, differential thermal analyzer/thermogravimetry, dilatometer, and impedance spectroscopy to study their structural, thermal, and electrical properties. The Rietveld refinement results confirmed that all the samples exhibit tetragonal structure with P4mm space group. In addition to this, sample x = 0.55 exhibits Ca ₂ Fe ₂ O ₅ as a secondary phase. It has been observed that lattice parameters decrease with increase in calcium content. The thermal expansion coefficient and ionic conductivity increases with increase in calcium content up to x = 0.50. The highest ionic conductivity is observed for Bi _0.5 Ca _0.5 FeO _3-y i.e. 1.71 × 10 ^-2 S cm ^-1 .