Thermal release of trapped electrons and phosphorescent decay in zinc silicate phosphors

Thermoluminescent (the glow curve) and phosphorescent decay experiments have been performed for a range of manganese activated zinc silicate phosphors. It is observed that the phosphorescent decay time is a nonmonotonic function of temperature when the light output is contributed simultaneously by two energetically adjacent traps. By representing the decay curve with exponential terms, the calculated trap depths can be correlated with the data obtained from the glow-curve experiment. Thus, the apparent contradiction between the relative insensitivity of the decay time with respect to temperature and the thermal activation of traps can be reconciled. In isolated traps, the decay time is always a monotonic function of temperature although the decay curve may not be exponential.