X-ray absorption near edge structure (XANES) spectroscopy technique is used to better understand the charging and decharging processes of the persistent luminescence in the Cr3+ doped AB2O4 spinels (A = Zn, Mg and B = Ga and Al) with low photon energy excitation by visible light. Cr K edge XANES spectra have been simulated for different near neighbour environments around the Cr3+ recombination centres and compared with the experimental curve. In Cr3+:ZnGa2O4 compound, the Cr3+ local structure corresponds mostly to that of a normal spinel (∼70\%), while the rest comprises of distorted octahedral environment arising from cationic site inversion and a contribution from chromium clustering. This local structure is strongly different in Cr3+:MgGa2O4 and Cr3+:ZnAl2O4 where, for both cases, chromium clustering represents the main contribution. The strong correlation between the intensity of persistent luminescence and \% of Cr in clusters leads us to infer that presence of Cr clusters is responsible for decrease of the intensity of the visible light induced persistent luminescence in the Cr3+ doped AB2O4 spinels.
@article{arxiv.1503.07979,
title = {Order and disorder around Cr$^{3+}$ in chromium doped persistent luminescence AB$_2$O$_4$ spinels},
author = {Neelima Basavaraju and Kaustubh R. Priolkar and Didier Gourier and Aurélie Bessière and Bruno Viana},
journal= {arXiv preprint arXiv:1503.07979},
year = {2015}
}