Hydrogen-induced phase transition in barium cerate.

The action of water vapor on nominally pure BaCeO[sub 3] perovskite at 850 K causes hydrogen to be incorporated into the lattice and a thermally metastable state to form. The lattice symmetry changes as a result of an orthorhombic-pseudocubic transition which takes place at a temperature substantially lower than the known thermally initiated rhombohedral-cubic transition at 1173 K. [ABSTRACT FROM AUTHOR]