Photoluminescence properties of Cr3+-doped MgAl2O4 natural spinel

We present, here, the results of a study of photoluminescence spectra of Cr3+-doped MgAl2O4 natural spinel in a given wavenumber range between 26,300 and 12,500 cm-1. By using several excitation sources, we observed a new broadband, namely K, with a peak at 15,547 cm-1 and the transition process of luminescence lines among the electronic levels of the Cr3+ ion, such as R, Ni (i = 1-4) lines. In terms of the experimental results and the configuration coordinates, we strongly propose that the K-band might originate from the electric dipole transition 2Eg 4A2g, in a strong crystal field with Dq/B 2.3. The decay-time and luminescence-rise-time curves on the zero-phonon lines and the K-band were also recorded.