It was recalled that spinel single crystals could be deformed plastically at high temperatures, and that the stress-strain curves often exhibited strong work-hardening; followed by prominent work-softening due to glide and climb processes. The critical resolved shear stress at a given temperature decreased markedly, by almost 2 orders of magnitude, with increasing deviation from stoichiometry. That is, as n increased from 1 to 3.5. The critical resolved shear stress was proportional to exp[-T/T0], and to [VC]-2, where T was the absolute temperature, T0 was a characteristic temperature, and [VC] was the concentration of charge-compensating cation vacancies. The Burgers vector was equal to ½<110>, and slip could occur on the {111} and {110} planes. The slip on {111} planes was believed to occur between the Kagome cation layer and the adjacent anion layer. Slip on {110} planes was slightly easier and had a higher T0 value because the planes were more widely separated. The temperature dependence of the critical resolved shear stress was explained in terms of the Peierls stress for partial dislocations; either in terms of a steep and high Peierls potential, or in terms of temperature- and stress-dependent kink diffusion. The dependence of the critical resolved shear stress upon [VC]-2 was explained in terms of kink nucleation at cation vacancies.

Dislocations and Mechanical Properties of MgO-Al2O3 Spinel Single Crystals. T.E.Mitchell: Journal of the American Ceramic Society, 1999, 82[12], 3305-16