The structure of δ-alumina evolved from the melt and the γ → δ transformation

Jayaram, V. ; Levi, C. G. (1989) The structure of δ-alumina evolved from the melt and the γ → δ transformation Acta Metallurgica, 37 (2). pp. 569-578. ISSN 0001-6160

Full text not available from this repository.

Official URL:

Related URL:


Electron diffraction patterns are used to analyze the structure of a metastable alumina (δ) found in powders <10 μm in diameter produced by atomization of molten Al2O3. The δ phase is believed to form directly from the liquid and also by solid state transformation of the cubic spinel γ. Both phases are based on an f.c.c. packing of anions with the interstitial cations having a higher degree of order in the δ phase. The γ → δ transformation begins with the ordering of tetrahedral cations in domains ~1-2 nm in size. The intensity distribution in reciprocal space indicates that the transformation is continuous from the spots of the disordered spinel, through diffuse scattering and finally the appearance of discrete superlattice reflections of the δ-phase. The δ is orthorhombic with crystal axes parallel to those of the parent spinel and unit cell dimensions that are simple multiples of the lattice parameter of γ. Two variants of the structure were observed with lattice parameters aδ = 2aγ, bδ = 1.5aγ, cδ = either aγ or 2aγ. The allowed reflections indicate a space group of P212121 for the structure with cδ = aγ, which is the more commonly observed.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
ID Code:63034
Deposited On:24 Sep 2011 14:59
Last Modified:24 Sep 2011 14:59

Repository Staff Only: item control page