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The physical basis of persistence luminescence in CaAl2O4 lattice based afterglow phosphors

In this paper we present the physical basis of persistence luminescence in CaAl2O4 lattice based afterglows phosphors. We demonstrate that the inherent presence of a set of three discrete trap levels at 0.65±0.01 eV, 0.70±0.01 eV and 0.77 ± 0.00 eV below conduction band give rise to the long period afterglow. Electron life time at RT (τ300) of these trap are determined as 10.71 ± 1.12 Minutes, 18.60 ± 3.93 Hours and 12.86 ± 2.76 Days. Trap deeper than these are also present that are irrelevant for persistence luminescence. Our conclusion is based on complete parameterization of trap levels in thermoluminescence (TL) of 253 nm UV excited nanocrystalline CaAl2O4. This has been possible by determination of the three key parameters namely activation Energy (E), frequency factors (s) and order of kinetic (b) using the deconvolution program of Chung.