in the course of searching for oxide ion conductors, perovskite oxides were synthesized by use of the conventional solid state reaction. The basic composition is Sr4In2Zr2O11, and the phase obtained shows a cubic perovskite structure indicating that the oxygen vacancies are disordered in this phase. The electrical conductivity of this material was estimated from ac impedance measurement, in the absence of the measurement of ionic transference number, and it was found to show the conductivity of 0.02 S cm(-1) at 1273 K. The conductivity was depressed by the substitution of Ga3+ for In3+ and Y3+ for Zr4+. (C) 2000 Elsevier Science B.V. All rights reserved.