Crystal structure of Ba27Fe16Ti33O117

Single-crystal X-ray diffraction studies indicate that the compound Ba27Fe16Ti33O117 crystallizes in the rhombohedral space group R3m, with a hexagonal unit cell a = 5.7400(8), c = 127.11(3) Angstrom: Z = 1.5. The arrangement may be described as a 54-layer (54L) close-packed structure (stacking sequence (cchcchhhhcchhhhcch)(3)) built from oxygen and {Ba, O} layers, with Ti4+ occupying octahedra and Fe3+ occupying both octahedral and tetrahedral interstices. The 54L structure contains hexagonal 6L BaTiO3-type (cch)(2) units via a 9-fold repeat of the 6L stacking sequence, with iron preferentially occupying layers centered a-round z = 1/6, Ba27Fe16Ti33O117 melts incongruently at 1270 degreesC and is difficult to purify in polycrystalline form, although crystals are easily obtained from partial melts. The new compound is a member of a family of ternary Ba-Fe-Ti-O phases that may be considered as dielectric-magnetic hybrids of barium-polytitanate and barium-hexaferrite crystal chemistries. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.