Preparation of Nd-doped BaCeO3 proton-conducting ceramics by homogeneous oxalate coprecipitation

Nd-doped BaCeO3 have been obtained from homogeneous coprecipitated oxalates when calcined at temperatures T greater than or equal to 1000 degrees C. Ball-milling of the calcined powders well disperses the agglomerates and consequently has a beneficial effect in the densification process. The calcination temperature has a major influence on the sintering process and powders calcined at 1100 degrees C possess good sinterabilities. The pressure applied to press the green pellets has no apparent influence on the sintered density at sintering temperatures of T greater than or equal to 1400 degrees C. By controlling the processing variables it was possible to obtain near fully dense Nd-doped BaCeO3 ceramics with homogeneous microstructure at a sintering temperature as low as 1300 degrees C. Electrical conductivities of the sintered samples were measured in dry and moist air and in hydrogen in the temperature range 500-800 degrees C using complex impedance techniques. Much higher proton conductivity was obtained in this work compared with previously reported values, in which the samples were prepared from traditional ceramic methods.