Crystal structures of solid solution (Ba1-xCax)(Sc1/2Nb1/2)O3 system

The solid solutions of (Ba1-xCax)(Sc1/2Nb1/2)O3(0 ≤ x ≤ 0.8) are synthesized in a wide composition range. In the present study, the crystal structures are determined by a synchrotron X-ray diffraction and an electron diffraction method. The crystal structure of Ba(Sc1/2Nb1/2)O3 (x = 0) has a cubic symmetry (Fm 3-bar m) with atomic parameters of about 0.8 nm (2 x 2 x 2 cells) judging by the appearance of very weak 111 reflections. The reflection intensity depends on the ordering in the B-cation. Furthermore, structural changes occur in the crystal symmetry, where the symmetries tend to decrease with increasing Ca content. This is controlled by the BO6 tilting system, since the cell sizes become smaller with increasing Ca content. Consequently, in the B-site, Sc3+ and Nb5+ ions come to have an orderly arrangement with increasing Ca content.