Luminescence properties of Ca4GdO(BO3)3:Eu in ultraviolet and vacuum ultraviolet regions

The luminescent properties of Ca4GdO(BO3)(3):Eu3+ were investigated under excitation of UV and VUV light. Separate two broad bands at around 259 and 184 nm were observed in the excitation spectrum of Ca4GdO(BO3)(3):Eu3+. These peaks were assigned to the charge transfer transition of Eu3+-O2- and Gd3+-O-2(-), respectively. Owing to the favorable spectral position in their broad intense excitation band, Eu3+ ions show a intense emission under 258 nm excitation in Ca4GdO(BO3)(3):Eu3+. This spectral position was determined by the free oxygen ions O (1). Ca4GdO(BO3)(3) doped with Eu3+ ion seems to be a preferable candidate as red lamp phosphor. On the other hand, a weak band with a maximum at about 184 nm was observed below 200 nm in the excitation spectrum of Ca4GdO(BO3)(3):Eu3+. This phosphor do not emit effectively under the 147 mn excitation. This unfavorable profile was also due to the 0 (1) ions, which played a role to the shifting towards the lower energy sides. The luminescence of Eu3+ ions in Ca4GdO(BO3)3 was somewhat different from that observed in the other borates phosphors, but resembled to those observed in the oxide phosphors (e.g. Gd2O3, Y2O3 and Gd2SiO5). Such behavior was recognized by the detailed analysis of crystallographical surroundings around activator. (C) 2003 Elsevier Ltd. All rights reserved.