Luminescence and fluorescence line narrowing studies of Y3Al5O12:Mn4+

A luminescence study of the Y3Al5O12:Mn4+ system is presented. Luminescence is due to 2E → 4A2 transitions on Mn4+ ions which substitute for Al3+ ions in distorted octahedral sites. The technique of fluorescence line narrowing (FLN) is used to interrogate some of the details of this transition. The zero-phonon R lines are found to be a composite of transitions from Mn4+ ions in different sites, the strongest line coming from Mn4+ ions in regular Al3+ sites. The ratio of R line to sideband in the emission from Mn4+ ions in these regular sites is found to be unusually low, and this is taken as an indication of an ion-lattice coupling for the Mn4+ ion which is significantly stronger than for the case of the Cr3+ ion in Y3Al5O12. Measurements of the luminescence decay rates as a function of temperature are given and we attempt to relate these data to models for nonradiative processes.