Visualization of stress distribution using mechanoluminescence from Sr3Al2O6: Eu and the nature of the luminescence mechanism

We have investigated the dependence of the mechanoluminescence intensity from Sr3Al2O6: Eu on compressive stress. The distribution of the mechanoluminescence intensity, which is clearly visible to the naked eye, is consistent with the calculated stress distribution. The luminescence centre has been identified as the Eu2+ ion from spectra of the mechanoluminescence and also from photoluminescence studies of Sr3Al2O6: Eu. The mechanoluminescence intensity decreases on repetitive application of stress but recovers completely on irradiation with ultraviolet light. The Sr3Al2O6: Eu is a p-type semiconductor and has hole traps of depth 0.11 eV. It is suggested that the mechanoluminescence mechanism arises from the movement of dislocations and recombination between electrons and holes released from these traps which are associated with Eu2+ centres.