Using mixed proton and oxide-ion conductor with BaCe~0~.~9Y~0~. ~1O~3~-~α as a solid electrolyte, hydrogen-air fuel cell was constructed. The performances of the cell were investigated at temperatures between 600 and 1000℃. The maximum short-circuit current density and the maximum power output density of this cell at 1000℃ were about 980mA·cm^-^2 and 0.22mW·cm^-^2, respectively. These performances were significantly better than those of other solid oxide fuel cells based on BaCe~0~.~9Y~0~.~1O~3~-~α(M=Sm, Gd, Yb, Nd, etc.) reported so far.

Key words: YTTRIUM OXIDE, CERIUM OXIDE, BARIUM OXIDE, SOLID ELECTROLYTE, FUEL CELLS, CERAMICS