Synthesis of zirconium titanate with an ordered M-fergusonite (beta) structure

摘要

We report a new zirconium titanate compound (Zr,Ti)O-2 with 27.5-35mol% titania (TiO2) formed from the oxides at 35-38 kbar, 1400-1500 degrees C. Crystal Structure investigations at atmospheric conditions with powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed a monoclinic Structure related to that of M-fergusonite (beta). Unit-cell dimensions (from 27.5 to 35mol% TiO2): a=7.267(20)-7.340(2)angstrom, b = 10.435(3)-10.429(1)angstrom, c = 5.023(11)-5.040(1)angstrom, beta = 136.45(12)-137.55(1)degrees, V = 262.44(92)-260.40(12)angstrom(3), Z=4. Rietveld refinement (R-F = 1.55) of a sample with 32.8 mol% TiO2 indicates that site A is 8-fold coordinated, mostly Occupied by Zr, while site B has 6-fold average coordination, occupied by Ti and Zr. Site B is Lit least partly ordered, as indicated by superstructure reflections 001 and -201 detected with TEM, reducing the space group from C2/c to C2. Pronounced streaking of selected diffraction spots is linked to the boundaries of lamellar domains in twin orientation, with twin planes either (200) or (20-2). Adjacent lamellae differ slightly in composition, causing subtle asymmetry of the twin diffraction patterns. (C) 2007 Elsevier Inc. All rights reserved.