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 fr om Sr(3)A1(2)O(6) : Eu on compressive stress. The distribution of the mecha noluminescence intensity, which is clearly visible to the naked eye, is con sistent with the calculated stress distribution. The luminescence centre ha s been identified as the Eu2+ ion from spectra of the mechanoluminescence a nd also from photoluminescence studies of Sr(3)A1(2)O(6) : EU The mechanolu minescence intensity decreases on repetitive application of stress but reco vers completely on irradiation with ultraviolet light. The Sr3A1206 : EU is a p-type semiconductor and has hole traps of depth 0.11 eV. It is suggeste d that the mechanoluminescence mechanism arises from the movement of disloc ations and recombination between electrons and holes released from these tr aps which are associated with EU2+ centres.