Cationic disorder effects in complex oxide laser materials and phosphors

A comparative analysis of the high-resolution spectra of the Nd3+ and Pr3+ in strontium lanthanum hexa-aluminates, charge compensated with magnesium Sr1−x(Nd, Pr)yLax-yMgxAl12−xO19, on a large composition range is presented. The spectra are mainly dependent on the composition parameter x and show two families of centers for x < 0.5 and three for x ⩾ 0.8, with distinct spectral characteristics. Based on spectral data, composition dependence and crystal structure, tentative structural models for the these centers are proposed. It is inferred that this complex picture results from the interplay between the effects determined by the anionic coordination of the centers and the perturbative effects caused by the multiple occupation of specific sites by cations of different valence.