On the orientation relationships in phase transformation of CaTiO3.

Electron Backscattering Diffraction (EBSD) is a well-known technique which is primarily used to analyse the microstructural features in metallic materials, including the orientation relationship between microstructural constituents. However, its versatility has not yet been critically utilized to establish crystallographic relationships involved in phase transformation of ceramics. In view of the significance of transformation twinning in ceramics on mechanical properties, the representative orientation relationships in twinned grains of CaTiO 3 is investigated using EBSD. It is observed that the matrix/twin pairs of CaTiO 3 have misorientation angles at 87°, 90° and 98°. The misorientations associated with the boundaries between twin/twin pairs formed by different twinning orientation relationships are noted at 90°, 91°, 92° and 98°. On the basis of the orientation relationships, the crystallography of cubic to orthorhombic and tetragonal to orthorhombic phase transformations in CaTiO 3 is explored. The most favorable orientation relationships pertaining to such a phase transformation are (001) o [ 100 ] o || (03 1 ¯ ) c [ 3 ¯ 13 ] c between parent cubic and daughter orthorhombic phases and (001) o [ 100 ] o || (1 1 ¯ 2 ¯ ) t [ 8 ¯ 2 ¯ 3 ¯ ] t between parent tetragonal and daughter orthorhombic phases of CaTiO 3. [ABSTRACT FROM AUTHOR]