Dislocation substructures in doped sapphire (α-Al < inf> 2 O < inf> 3 ) deformed by basal slip

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The dislocation substructures in sapphire (α-Al2O3) doped with isovalent (Cr3+ and Ti3+) and aliovalent (Ti4+ and Mg2+) solutes and deformed by basal slip at 1500-1520°C have been studied by transmission electron microscopy. The dislocation substructures in the Cr3+- and Ti3+-doped sapphire are similar to those in undoped sapphire; however, the aliovalent solutes (and their associated charge-compensating defects) cause changes in the dislocation substructures, particularly in the density and distribution of small dislocation loops produced by breakup of dislocation dipoles. Very few loops are present in Mg2+-doped sapphire, while prominent strings of loops are present in Ti4+-doped sapphire, although only at small strains. These and additional changes in the dislocation substructures are attributed to an increase in the bulk diffusion kinetics on doping with Mg2+ and a decrease in the bulk diffusion kinetics on doping with Ti4+. © 1982.

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Acta Metallurgica