Phase equilibria in the La-Ba-Co-O system

Phase equilibria in the La-Ba-Co-O system were studied at 1100 degrees C in air. The existence of oxide phases LaCoO3, BaCoO3-y, Ba2CoO4, and La2BaO4 in quasibinary systems in air at 1100 degrees C was found, in agreement wit h previous data. Two types of solid solutions were found in the quasiternar y system: La1-xBaxCoO3-delta and (La1-zBaz)(2)CoO4. The homogeneity range o f La1-xBaxCoO3-delta was found to be 0 less than or equal to x less than or equal to 0.8. As the content of alkali-earth metal (x) increased, a rhombo hedral distortion of La1-xBaxCoO3-delta de creased; La0.55Ba0.45CoO3-delta had an ideal cubic structure. The composition of single phase samples of (L a1-zBaz)(2)CoO4 composition was obtained for z = 0.300, 0.325, 0.350, and 0 .375. These samples had the tetragonal K2NiF4-type structure. (C) 1999 Else vier Science Ltd.