Triboluminescence of alkaline earth aluminate polycrystals doped with Dy3+

Triboluminescence spectra have been measured for polycrystalline (Sr,Ba)Al2O4 and (Sr,Ca)Al2O4 doped with Dy3+. Sr1-xBaxAl2O4:Dy3+ with x = 0, 0.1, 0.2, and 0.4 and Sr0.9Ca0.1Al2O4:Dy3+ clearly exhibit triboluminescence caused by the 4f-4f transitions of Dy3+. In contrast, triboluminescence is barely observed in Sr0.8Ca0.2Al2O4:Dy3+ and Sr0.6Ca0.4Al2O4:Dy3+ although both of them show photoluminescence due to the 4f-4f transitions of Dy3+. For the Sr1-xBaxAl2O4:Dy3+ with x = 0, 0.1, 0.2, and 0.4 and Sr0.9Ca0.1Al2O4:Dy3+, the compositional dependence of the relative integrated intensity of the emission lines is different between triboluminescence and photoluminescence spectra. We suggest two possibilities to explain this phenomenon; one of them is the self-absorption by Dy3+ in the case of triboluminescence, and the other is a situation that a strain is imposed on Dy3+, which brings about the triboluminescence due to the 4f-4f transitions. We speculate that the latter is the main cause for the difference between triboluminescence and photoluminescence spectra. (C) 2000 American Institute of Physics. [S0021-8979(00)03020-6].