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.