Unusual luminescence and temperature dependent decay behavior of divalent europium ion in KBaBP2O8

The unusual photoluminescence (PL) properties and temperature dependent decay behavior of Eu2+ in KBaBP2O8 are reported and discussed. The emission spectrum is so complicate that it can be deconvoluted into three fitting peaks. The emission bands peaking at 380 and 444 nm can be assigned to the 4f65d1→4f7 transition of Eu2+ centers substituting for K+ and Ba2+ site, while the emission band at 497 nm may be attributed to the Eu2+ center on K+ site with a nearby charge-compensated vacancy. The decay time of the 4f65d emission increases with temperature. This increase can be explained by either thermal population of the 4f7 (6P7/2) level or thermal population of higher energetic 4f65d states.