Fully stabilized zirconia solid solutions (s.s.) containing manganese seem to be promising materials for intermediate layers between electrolytes and cathodes in solid oxide fuel cells. When manganese is present in zirconia solid solutions, they start to exhibit electronic conductivity due to the formation of some electronic defects related with the variable valence of manganese and, in consequence, activation losses that accompany the transfer of charge between electrolyte and cathode may be reduced. Powders from Mn-x(Y0.148Zr0.852)(1-x)O2-delta (with x ranging from 0 to 0.25) materials were prepared by means of the co-precipitation-calcination method and then sintered for 2 h at 1500 degrees C. The compositional dependence of the lattice parameters complied with Vegard's rule up to about 18 mol% of manganese, which confirmed that cubic zirconia s.s. had been formed. The bulk conductivity of the samples and their grain boundaries, determined using impedance spectroscopy, are strictly dependent on their chemical composition. The observed changes in the concentrations of ion and electron defects in cubic zirconia may be utilized in the construction of solid oxide fuel cells. (C) 2009 Elsevier B,V. All rights reserved.