Pre-treated LSGM starting powders decrease in particle size, leading to an increase in the LSGM relative density and electric conductivity. The starting powders are ball-milled with the assistance of absolute ethanol to reduce the particle size, dried ultrasonically to prevent the agglomeration of the powders and pre-calcined and re-balled to increase the rate of grain growth. These improvements make it possible to obtain single phase LSGM powders with small particle size at the calcination temperature of 1300 degrees C. A large-area (9 cm x 9 cm) LSGM electrolyte substrate has been prepared successfully by tape casting from these powders. The LSGM electrolyte exhibits a dense structure, the relative density reaches 96%, and the electrical conductivity is 0.08 S cm(-1) at 800 degrees C. (C) 2010 Elsevier B.V. All rights reserved.