Defect induced photoluminescence and triboluminescence in layered CaLaAl3O7

In this work, a layered melilite structure, CaLaAl3O7, was synthesized and observed to have obvious luminescence behaviors under the stimuli of ultraviolet light and rubbing, which were called photoluminescence and triboluminescence, respectively. Considering the wide bandgap of CaLaAl3O7 and its specific crystal structure, the observed luminescence should be attributed to intrinsic defects. Both the photoluminescence and triboluminescence of CaLaAl3O7 show a strong dependence on the synthesis atmosphere, suggesting that they should be related to the oxygen vacancy. It is attractive to find that the triboluminescence of CaLaAl3O7 shows a distinct spectral characteristic compared to its photoluminescence. Further computational results suggest that the applied mechanical stimuli on the CaLaAl3O7 cell could promote the formation of the vacancies of oxygen and calcium, responsible for the spectral differences.