A new metastable alumina polymorph with monoclinic symmetry

Publisher Website
Google Scholar
Abstract
Polymorphic phase transitions between alumina structures based on fcc packing of oxygen have been studied by electron diffraction and highresolution electron microscopy. A new metastable alumina polymorph with monoclinic symmetry was identified in alumina obtained by both plasma spraying and thermal oxidation of aluminium. The structure of this phase was described by the P 2 / c space group and a unit cell containing 32 formula units 1 with lattice parameters a = 8.45 A, b = 16 A, c = 12.64 A and beta = 115o. It is suggested that the new phase is evolved from cubic gamma-Al O by ordering of 2 3 aluminium cations on interstitial sites of the fcc packed oxygen sublattice. The transformation proceeds through an orthorhombic distortion of the cubic anion structure. Crystallographic domain and interdomain boundaries in lambda-Al O were 2 3 identified and related to the symmetry changes which accompany gamma lambda phase transition.

This publication has 0 references indexed in Scilit: