Accommodation of impurities in α-Al2O3, α-Cr2O3 and α-Fe2O3

Oxygen vacancy diffusion in alumina: New atomistic simulation methods applied to an old problem

“…At the temperatures considered in this work (1400-2200 K), intrinsic diffusion will not be significant, as can be illustrated by looking at the defect formation energies. The formation energy for an oxygen vacancy is known to be about 5 eV per defect for either Frenkel or Schottky disorder [4][5][6][7][8][9]; the potentials used in the present work predict the lowest energy to be the Frenkel defect with 4.6 eV per defect. This means that in the temperature range of interest (1400-2200 K) the atomic fraction of intrinsic vacancies is of the order of 10 À17 -10 À11 .…”

“…The formation of oxygen vacancies by intrinsic Schottky and Frenkel defects has been studied by many authors [4][5][6][7][8][9] using computational methods. The reported formation energies per defect for the Schottky defect range from 4.18 to 5.86 eV and from 3.79 to 8.27 eV for the anion Frenkel defect.…”

Effects of the Microstructure Induced by Sintering on the Dielectric Properties of Alumina

“…Simulation results show that the formation energies of intrinsic point defects in α-alumina are relatively high (Atkinson et al, 2003). They are estimated respectively for Schottky defects, cation Frenkel and anion Frenkel at 5.15, 5.54 and 7.22 eV.…”

“…In the case of a cation (M) greater in valence than the host cation (Al 3+ ), the dissolution mode in substitutional position is most likely the cationic vacancy compensation mechanism (Atkinson et al, 2003). Accordingly, for tetravalent cations, in MO 2 (such as SiO 2 or TiO 2 ), the dissolution reaction is:…”

“…For divalent cations, in MO (such as MgO or CaO), the anionic vacancy compensation of substitutional ' Al M , is suggested (Atkinson et al, 2003):…”