The role of the A-site cation and crystal structure on the electrical conductivity of strontium-doped calcium and barium manganites

The influence of A-site cation doping, crystal structure and structural defects (oxygen nonstoichiometry) on the electrical conductivity of Sr-doped CaMnO3 (CSMO) and BaMnO3 (BSMO) was investigated. CSMO and BSMO were prepared by citrate-nitrate autocombustion and coprecipitation synthesis, pressed into pellets and sintered. Since the oxygen nonstoichiometry in CSMO was uniform, the increase in electrical conductivity was primarily caused by the increase in Sr content. On the other hand, the oxygen nonstoichiometry in BSMO was more pronounced and it decreased with Sr- doping. Therefore, the highest conductivities were obtained for the undoped BaMnO3 samples. The electrical conductivities of CSMO were similar to those of widely investigated rare-earth manganites and more than 10^4 times higher than those of BSMO. Therefore, CSMO has the potential to be a low-cost cathode material in solid oxide fuel cells.