Luminescence in deformed MgO, CaO and SrO

Abstract

Plastic deformation in the alkaline-earth oxides results in optical absorption bands, the most pronounced of which occur at 5–7 eV in MgO, 4–6 and ∼5–8 eV in CaO, and 4–1 and ∼5–0 eV in SrO. Excitation in these energy regions generates luminescence bands, with peaks at 2–9 (violet), 2–6 (blue), and 2–3 (green) eV in MgO, CaO and SrO, respectively. The temperature- and anisotropy-dependence of the emission spectra gives clear indications that multi-bands are involved. The visible emission provides a convenient means of observing slip systems without artificial decoration techniques. Correlation between emission intensity pattern and dislocation etch-pit density has been demonstrated in MgO. The luminescence effect permits an instantaneous and clear observation of gross imperfections as they are being formed in a solid, either on the surface or in the bulk. Dynamic studies of dislocation interaction can be made. By monitoring the emission intensity as a function of stress and strain, it was found that the defects responsible for the emission are formed at the onset of plastic deformation.