Electron paramagnetic resonance and luminescence properties of Eu2+ in oxyfluoride barium borate glasses

Abstract

The Eu-doped xBaO-(100-x)B2O3 and xBaF2-(100-x)B2O3 glasses were prepared by melting method under a reducing atmosphere, exhibiting broadband luminescence peaks of 4f65 d1→4f7 in the excitation range of 300–400 nm. PL, EPR, and XPS were used to analyze the effects of the Ba2+, F−, and Eu ion content on the Eu2+/Eu3+ ratio and Eu2+ emission wavelength and intensity. An excess of Ba2+ ions with a high optical basicity reduced the Eu2+/Eu3+ ratio and enhanced the ligand field strength surrounding the Eu2+ ions, decreasing the Eu2+ luminescence intensity and red-shifting the luminescence peak. The addition of F− had the effect of diminishing the optical basicity, decreasing the OH groups content and eliminating Eu2+ clusters, which not only mitigated the effects of the Ba2+ ions, but also significantly enhanced the luminescence intensity of Eu2+ ions. An increase in the Eu ion concentration led to a red-shift in the Eu2+ fluorescence, which was attributed to the nephelauxetic effect. Therefore, the luminescence color of these glass samples could be manipulated by adjusting the doping concentrations of Ba2+, F−, and Eu2+.