The Temperature Dependence of Rare‐Earth Activated Garnet Phosphors: I . Intensity and Lifetime Measurements on Undoped and Ce‐Doped

The temperature dependence of cathodoluminescence intensity and decay time in the range 10°–480°K is reported for both nominally pure and Ce 3+ ‐doped yttrium aluminum garnet (YAG) crystals. Luminescence from characteristic lattice defect levels and from the 2 D excited state of the Ce 3+ impurity have both been investigated. Three lattice defect levels have been detected. Recombination is dominated by the shallowest centers at low temperatures but, at higher temperatures, thermalization effects reduce the net capture rates at the competitive defect centers. As a result of thermalization in the doped crystal the efficiency of energy transfer to Ce 3+ is increased, but only at the expense of introducing a long afterglow into the Ce 3+ decay near room temperature. The temperature‐dependent interactions between different centers in the lattice are adequately described by a simple kinetic model. Each center is characterized by three rate processes and by a thermalization activation energy which is derived from the decay time data. The experimental results are in good agreement with preliminary studies already reported by the authors.