A new calcium iron(II) titanate ordered perovskite, CaFeTi2O6, synthesized at 12-15 GPa and 1200-1400°C has been studied using convergent beam electron diffraction (CBED) and high-resolution transmission electron microscopy (HREM) techniques. CBED and selected area diffraction (SAD) patterns confirm that CaFeTi2O6 is tetragonal with a = 7.51 ± 0.02 Å, c = 7.54 ± 0.02 Å. The tetragonal structure is consistent with the symmetry of P42/nmc proposed on the basis of X-ray diffraction studies. A CaFeTi2O6 crystal was studied at both ambient temperature and 84 K. In situ experiments show no phase transformation upon cooling. High resolution imaging and nanobeam analysis reveal three types of morphology. In addition to the major nearly perfect perovskite phase, this material contains two sizes of iron precipitates. One size class averages 4 nm in diameter and the other 15 nm in diameter. Crystalline perovskite-like domains with a high degree of disorder were also observed. The formation of this type of domain may be related to local variations of stoichiometry with considerable oxidation. The coexistence of reduced and oxidized regions in the same specimen is noteworthy, and probably indicates incomplete equilibration during high pressure Synthesis.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry