Investigations were made of the compressive-stress dependence of the mechanoluminescence intensity from Eu-doped samples. The distribution of the clearly visible mechanoluminescence intensity, which was clear to the naked eye, was consistent with the calculated stress distribution. The luminescence centre was identified as being the Eu 2+ ion. The mechanoluminescence intensity decreased during repetitive application of stress, but recovered completely upon irradiation with ultraviolet light. It was suggested that the mechanoluminescence mechanism arose from the movement of dislocations and recombination between electrons and from holes which were released from these traps that were associated with Eu2+ centres.

Visualization of Stress Distribution using Mechanoluminescence from Sr3Al2O6:Eu and the Nature of the Luminescence Mechanism. M.Akiyama, C.N.Xu, M.Taira, K.Nonaka, T.Watanabe: Philosophical Magazine Letters, 1999, 79[9], 735-40