Oxygen ionic transport in dense LaGa0.65Ni0.20Mg0.15O3-delta membranes, prepared by the standard ceramic synthesis technique and via glycine-nitrate process (GNP), was studied using measurements of the total conductivity, oxygen permeation and faradaic efficiency (FE). At 1223 K oxygen transfer through LaGa0.65Ni0.20Mg0.15O3-delta ceramics is mainly determined by the bulk ambipolar conductivity, while decreasing temperature leads to a greater role of the surface exchange rate. In spite of moderate difference in the ceramic microstructures, the surface exchange limitations are considerably higher for the membranes prepared by the standard ceramic route compared to GNP-synthesized material. Thermal expansion and partial ionic and electronic conductivities were found essentially independent of the synthesis method. The level of oxygen ionic conduction in LaGa0.65Ni0.20Mg0.15O3-delta, characterized by the activation energy of about 150 kJ/mol and ion transference numbers in the range 1 X 10(-3) -5 x 10(-2) at 973-1223 K, is higher than that in La(Ga,Ni)O3-delta perovskites and comparable to La2NiO4-based phases. (C) 2002 Elsevier Science Ltd. All rights reserved.