K. Leinenweber et J. Parise, HIGH-PRESSURE SYNTHESIS AND CRYSTAL-STRUCTURE OF CAFETI2O6, A NEW PEROVSKITE STRUCTURE TYPE, Journal of solid state chemistry, 114(1), 1995, pp. 277-281
Single-crystal and powder samples of a new calcium iron (II) titanate,
CaFeTi2O6, have been synthesized at 12-15 GPa and 1200-1400 degrees C
, and studied by X-ray diffraction. This compound is a variant of the
perovskite structure and crystallizes in the tetragonal space group P4
(2)/nmc, a = 7.5157(2) Angstrom, c = 7.5548(2) Angstrom, and Z = 4. Ca
lcium and two iron atoms are ordered on three different A sites, with
calcium in approximately 10-fold coordination, with one iron atom in t
etrahedral coordination (Fe-O = 2.084(2) Angstrom), and the other iron
atom in square-planar coordination (Fe-O = 2.097(2) Angstrom). The sy
stem of octahedral tilts which this compound adopts has not been obser
ved previously in a perovskite. The tilt system was described in a the
oretical treatment of perovskites (a(+)a(+)c(-) in the notation of A.
M. Glazer (Acta Crystallogr. Sect. B 28, 3384, 1972) and was (incorrec
tly) assigned to space group Pmmn. (C) 1995 Academic Press, Inc.