Effects of Cr3+ concentration on the optical properties of Cs2NaAlF6 single crystals

This work is devoted to the study of optical properties of the elpasolite Cs2NaAlF6 with 0.1, 1.0, 3.0, 10.0, 30.0 and 50.0% of Cr3+ ions. The interest in this system lies on the fact that it presents a high quantum yield in the visible and infrared regions and therefore can be considered for laser applications. The photoluminescence and excitation spectra were obtained at 5 and 300 K, while the absorption spectra were measured at 300 K. The spectra at 300 K show broad bands attributed to the Cr3+ ions in two non-equivalent sites, both of them with octahedral coordination, while at 5 K we can observe the vibrational modes of the [CrF6]3− complex. The ensemble of our results lead us to conclude that the material has potential applications as a lasing system.