Patent ID: 7368095

Claim:
A composite oxide for a solid oxide fuel cell having a perovskite type crystal structure represented by the following formula: Ln 1-X A X Ga 1-Y-Z B Y C Z O 3-δ (1) wherein Ln is at least one element selected from the group consisting of lanthanium, cerium praseodymium, neodymium, samarium, gadolinium, dysprosium, and mixtures thereof, A is at least one element selected from the group consisting of strontium, calcium, barium, and mixtures thereof, B is at least one element selected from the group consisting of magnesium, aluminum, indium, and mixtures thereof, and C is at least one element selected from the group consisting of iron, cobalt, nickel, manganese, and mixtures thereof, 0.05≦x≦0.4, 0.02≦y≦0.4, 0.1≦y+z≦0.45, 0≦δ≦1, and the heterogeneous phases, which are different from the phase having a perovskite structure, are present in an amount such that the average area ratio of heterogenous phase to the phase having perovskite structure is at most 0.3%, the weight-average particle diameter of the composite oxide is from 0.4 to 2 μm, and the tap density is at least 1.0 g/cm 3 .