Phase transition and fluorescence regulation of BaAl2Si2O8:Eu using Ba source

Abstract

In this investigation, BaAl2Si2O8 (BAS):Eu2+ (BaF2-derived BAS:Eu and BaCO3-derived BAS:Eu) series of blue phosphor samples were synthesized through high-temperature solid-phase method, and their structure and luminescence properties were examined. In the case of BaF2-derived BAS:Eu, hexagonal feldspar (BaAl2Si2O8) was obtained, which exhibited a UV region (λem = 372 nm) fluorescence at 300 nm excitation. In the case of BaCO3-derived BAS:Eu, a monoclinic feldspar (BaAl2Si2O8) was obtained, which exhibited a blue region (λem = 428 nm) fluorescence at 300 nm excitation. The luminescence mechanism was the f-d transition of Eu2+, and the Eu2+ underwent different degrees of 5 d energy level splitting in different crystal field environments. This accounted for the UV region and blue region fluorescence. Considering that the phase transition between the hexagonal and monocline phases is a slow process, fluorescence emissions in UV and blue regions were generated during the two-phase transition period. As a result, phosphor exhibited a controllable spectrum from UV region (λem = 372 nm) to blue region (λem = 428 nm). Furthermore, based on the crystal field splitting formula, the blue-shift phenomenon of the spectrum was shown to occur in the monoclinic phase. Finally, the crystal distortion index of the environment of Eu2+ was calculated.