Abstract
Deep red persistent luminescence properties of Cr3+ activated LaAlO3 phosphors were investigated. The variation of lanthanide codopants, Sm3+, Eu3+, Tm3+ on thermoluminescence (TL) glow curves suggests an electron trap model of persistent luminescence in LaAlO3:Cr3+ phosphors. Between lanthanide cations, Sm3+ was found to be a good codopant for enhanced persistent luminescence. TL excitation spectrum showed only a UV band similar to that of photoluminescence excitation which are attributed to 4A2→4T1(4P). Based on the structure and intensity of TL glow curves after different wavelength excitation, it is found that the efficient charging through conduction band and inefficient local charging occur under UV and blue excitation, respectively.
Highlights
Persistent phosphors show delayed luminescence which continues several seconds to several tens of hours after ceasing excitation light
These materials have been developed for application for safety signs
The advantage of persistent phosphors for imaging application is that the material is used after ultraviolet
Summary
Persistent phosphors show delayed luminescence which continues several seconds to several tens of hours after ceasing excitation light. These materials have been developed for application for safety signs as well as in vivo imaging application [1,2,3,4,5]. Cr3+ activated LaAlO3 compound shows zero phonon lines (R-line, 2E→4A2 transition) at 734 nm at longer wavelength compared with other well-known Cr3+ activated oxides, for instance 694 nm in Al2O3 and in ZnGa2O4. The TL glow curves by various charging excitation wavelength and persistent luminescence decay curves at different temperatures were analyzed for the mechanism of charging and detrapping processes.
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