Studies of BaO–In 2O 3–CuO ternary system : Part II: crystallochemical characterization of the (β)-solid solution

Abstract

A detailed crystallochemical characterization of the (β)-phase found in BaO–In 2O 3–CuO ternary system at 930°C is presented. The phase originates from binary terminal Ba 2In 3O 6.5 (Ba 1.6In 2.4)O 5.2 and expands into the ternary system as a triangularly shaped domain, resulting from a double substitution of the (Ba 1.6+ m In 0.4− m )(In 2− n Cu n )O 5.2−( m+ n)/2 type. The phase exhibits an already characterized crystal structure, known as the ‘doubled’ perovskite type, which was earlier ascribed to Ba 2InCuO 4.5 and to the series of Ba 2In 2− x Cu x O 5−Δ type solid solution. Based on a comparison of the experimental sample densities with those calculated for several models of possible 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 (β)-phase. However, on crossing the above mentioned concentration, an increasing number of vacancies appear in its (In+Cu) sublattice (the perovskite B-site), thus additionally increasing the overall structure deficiency. In spite of this, stability of the crystal structure increases.