The Ruddlesden-Popper (R-P) oxides Sr3.2-xCaxLn0.8Fe1.5Co1.5O10-δ with x = 0 and 0.4 and Ln = La, Pr, and Nd, have been synthesized and the effect of Ca on their electrochemical properties as cathodes in solid oxide fuel cells (SOFC) has been investigated. The substitution of Ca for Sr in Sr3.2-xCaxLn0.8Fe1.5Co1.5O10-δ decreases the amount of oxygen loss on heating and the thermal expansion coefficient (TEC). The phase instability of these materials at high temperature is a significant issue that restricts their application as SOFC cathodes, and the substitution of Ca effectively stabilizes the Sr3.2-xCaxLn0.8Fe1.5Co1.5O10-δ phase at 800°C. Among the different lanthanides with and without Ca in Sr3.2-xCaxLn0.8Fe1.5Co1.5O10-δ, the Ln = Nd samples exhibit an enhancement in cathode performance in SOFC compared to Ln = La and Pr samples, which may be attributed to the higher concentration of oxygen vacancies in the Ln = Nd samples. Comparing the various compositions studied, the Sr2.8Ca0.4Nd0.8Fe1.5Co1.5O10-δ cathode material exhibits superior performance in SOFC with good phase stability.