CRYSTAL-STRUCTURE OF BA2SCALO5 AND SR2SC0.5AL1.5O5

Single crystals of (I) Ba2ScAlO5 and (II) Sr2Sc0.5Al1.5O5 were prepared by high temperature reactions and investigated by the X-ray technique. (I) belongs to the BaTiO3 type (a = 5.7965 angstrom; c = 14.5398 angstrom; space group, D6h4 (P6(3)/mmc); Z=3) and (II) show a cubic perovskite structure (a = 7.9078 angstrom; space group, T(h)6 (Pa3BAR); Z = 4). The reinvestigation of (I) shows only one underoccupied point position of O(2). The substitution of Ba2+ by Sr2+ changes the 6L-type structure of (I) to the classic cubic perovskite with partially ordered occupation of octahedra holes of (II).