The Effects of Crystal Field and Temperature on the Photoluminescence Excitation Efficiency of Ce3+ in YAG

Absorption and luminescence spectra of YAG:Ce 3+ crystals have been measured at various temperatures between 4.2° and 300°K. The high resolution, low temperature spectra show resolved fine structure. Zero‐phonon transitions have been assigned and the phonon replicas correlated with lattice phonon energies. The characteristic absorption band of YAG:Ce 3+ near 460 nm decreases in intensity, whereas that near 340 nm increases with increasing temperature. This effect is explained in terms of a tetragonal crystal field splitting of both the 4f 1 ground state and 5d 1 excited states of Ce 3+ in YAG. When allowance is made for changes in the absorption of pump light with temperature the photoluminescence quantum efficiency of Ce 3+ in YAG is constant up to 300°K. The significance of these crystal field effects for the use of YAG:Ce as a high temperature lamp phosphor is discussed.