Studies of BaO-In2O3-CuO ternary system Part I: Phase equilibria in the isothermal cross-section of 930 degrees C

Phase equilibria in the BaO-In2O3-CuO ternary system at 930 degrees C have been determined. Of all the binary and ternary compounds of this system rep orted in the literature, the existence of some of them has been confirmed a t 930 degrees C, namely; In2Cu2O5, Ba-deficient BaCuO2, Ba5In2O8 and/or Ba4 In2O7. The latter two have been identifed by us as a single phase of variab le composition Ba5-xIn2+xO8+0.5x (alpha-phase) with 0 less than or equal to x less than or equal to 0.45, then Ba3In4Cu3O12 and Ba2In3O6.5, the latter denoted as Ba1.6In2.4O5.2 to reflect its 'doubled' perovskite structure - different from that reported to date for the Ba2In3O6.5 compound and identi cal to the already described series of Ba2In2-xCuxO4+Delta type. The 'doubl ed' perovskite Ba1.6In2.4O5.2 presents the origin of a triangularly shaped ternary solid solution, (beta-phase), which penetrates the BaO-In2O3-CuO tr iangle along a direction, roughly describable with the formula Ba1.6+xIn2.4 -2xCuxO5.2-x with 0 less than or equal to x less than or equal to similar t o 0.6. A satisfactory explanation concerning mutual relation of the Ba2In2- xCuxO4+Delta type series and the beta-phase is given. Finally, a new ternar y phase of the composition Ba6-xInxCu2O8+0.5x, 0.7 less than or equal to x less than or equal to 1, has been found and its symmetry and lattice parame ters determined. (C) 2000 Elsevier Science S.A. All rights reserved.