Studies of BaO-In2O3-CuO ternary system Part II: crystallochemical characterization of the (beta)-solid solution

A detailed crystallochemical characterization of the (beta)-phase found in BaO-In2O3-CuO ternary system at 930 degrees C is presented. The phase origi nates from binary terminal Ba2In3O6.5 (Ba1.6In2.4)O-5.2 and expands into th e ternary system as a triangularly shaped domain, resulting from a double s ubstitution of the (Ba1.6+mIn0.4-m)(In2-nCun)O5.2-(m+n)/2 type. The phase e xhibits an already characterized crystal structure, known as the 'doubled' perovskite type, which was earlier ascribed to Ba2InCuO4.5 and to the serie s of Ba2In2-xCuxO5-Delta type solid solution. Based on a comparison of the experimental sample densities with those calculated for several models of p ossible distribution of the M-structure components it was shown that up to 50 at.% Ba, only oxygen deficiency persists in the crystal structure of the (beta)-phase. However, on crossing the above mentioned concentration, an i ncreasing number of vacancies appear in its (In+Cu) sublattice (the perovsk ite B-site), thus additionally increasing the overall structure deficiency. Tn spite of this, stability of the crystal structure increases. (C) 2000 E lsevier Science S.A. All rights reserved.