Warm-white persistent luminescence of Lu3Al2Ga3O12:Pr3+ phosphor

A warm-white emitting persistent luminescence phosphor Lu3Al2Ga3O12:Pr3+ was synthesized by solid state method at 1600 degrees C in air. The refined crystal structure of Lu3Al2Ga3O12 host was solved by X-ray diffraction (XRD). The photoluminescence spectra, decay curve and thermoluminescence were investigated. It was revealed that the persistent luminescence originated from the f-f transitions of Pr3+ emitters at Lu3+ sites in LuO8 polyhedrons and it showed white color due to the P-3(0) -> H-3(4), P-3(1)-> H-3(8),(P0 -> H8)-P-3-H-3 ,P-3(0) -> H-3(6),P-3(0)-> F-3(2),(P0 -> F3)-P-3-F-3 and P-3(0)-> F-3(4) transitions of Pr3+ emitters in a wide range. The persistent luminescence of Pr3+ in this host could be promoted by f-d transition (278 nm) but f-f transitions due to the different thermal activation energy. The persistent luminescence of the optimal sample could be actually recorded for 3 h by the definition of 0.32 mcd/m(2) and was visible for more than 7 h by dark-adapted vision in darkness. The initial depth of the dominant shallow traps was calculated to be about 0.56 eV which is suitable for persistent luminescence. The different roles of the shallow and deep traps on the persistent decay process were investigated. Accordingly the persistent luminescence processes and mechanism of the as-synthesized Lu3Al2Ga3O12:Pr3+ phosphors were proposed.