La0.9Sr0.1Ga0.8M0.2O3-delta (M = Mn, Co, Ni, Cu or Zn): Transition metal-substituted derivatives of lanthanum-strontium-gallium-magnesium (LSGM) perovskite oxide ion conductor

Perovskite oxides of the general formula, La0.9Sr0.1Ga0.8M0.2O3-delta for M = Mn, Co, Ni, Cu and Zn, have been prepared and investigated. All the oxid es exhibit high electrical conductivities (sigma similar to 10(-2) S/cm at 800 degrees C) comparable to that of the best perovskite oxide ion conducto r, La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) (sigma similar to 8 x 10(-2) S/cm at 80 0 degrees C), While M = Mn, Co, Ni, Cu members appear to be mixed conductor s with a variable electronic contribution to the conductivity, especially a t high oxygen partial pressures (pO(2) greater than or equal to 1 atm), ari sing from mixed-valency of the transition metals, the M = Zn(II) phase is a pure oxide ion conductor exhibiting a conductivity (sigma similar to 1.5 x 10(-2) Slcm at 800 degrees C) that is slightly lower than that of LSGM. Th e lower conductivity of the M = Zn(II) derivative could be due to the prefe rence of Zn(II) for a tetrahedral oxygen coordination.