Stationary SOFCs are source of green electricity to power future electrically powered vehicles. In SOFC the ionic conductivity determines the efficiency. It is obvious that a shift in the operating temperature of solid oxide fuel cells (from 1000 down to around 750–800 degree C) is desired. However, better electrolyte and electrode materials are required for lower temperature operation in order to maintain their high temperature performance. It had been known that both phase purity (single phase) and microstructure of, for example LSGM materials, depend on synthesis procedure and processing and, as a matter of fact, the synthesis of a pure single phase material is rather difficult [1,2].

Two important conclusions are the objective of this research work:

1-The cathode, anode or electrolyte become ionically conducting at a sharp phase transition temperature (the operating T of the SOFC). Below such T the materials loses its ionic conductivity [3]

2-The Gibbs phase rule (single phase and two components of the air) may be applied at the triple phase boundary (TPB) where the number of phases of the MIEC (single or two phases) are in contact with single and pure phase electrolyte [4].

1. Djurado, E. and Labeau, M., J. Europ. Ceram. Soc., 1998, 18, 1397–1404

2. Tas, A. C., Majewski, P. and Aldinger, F.,. J. Am. Ceram. Soc., 2000, 83, 2954–2960

3. S. Hall, Superionics: crystal structures and conduction process,.Rep. Prog Physics, 2004, 67, 1233-1314

4. S. B. Adler, Factors Governing Oxygen Reduction in Solid Oxide Fuel Cell Cathodes, Chem. Rev. 2004, 104, 4791−4843.