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PrGaO3-based perovskite oxides were synthesized using a standard solid state technique. In the formula Prt-xMxGa1-yMgyO3 (M = Ca, Sr), the solid solution limit is x = 0.1 for Ca/Sr doped at A sites and y = 0.2 for Mg doped at B sites. Thr oxygen ion conductivity increases and the activation energy decreases with increasing dopant concentration at A sites or B sites by single doping. However, the conductivity decreases when both A and B sites are doped, compared with single doping only. Mg-doped samples have superior properties, i.e. PrGa0.9Mg0.1O3 has a maximum conductivity of 0.05 S/cm at 800 degreesC, while PrGa0.8Mg0.2O3 has a minimum activation energy of 24.19 kJ/mol in all the samples. With increasing temperature, the oxygen ion transport number of the samples increases. The conductivity of these samples is mainly ionic although hole conduction was observed. A power density of 0.131 W/cm(2) and a short circuit current density of 0.45 A/cm(2) were obtained at 940 degreesC in the fuel cell experiment by using PrGa0.9Mg0.1O3 as an electrolyte. (C) 2001 Elsevier Science B.V. All rights reserved.