Identification of charge transfer (CT) transition in (Gd,Y)BO 3:Eu phosphor under 100–300 nm

Abstract

A broad excitation band in an excitation spectrum of (Gd,Y)BO 3:Eu was observed in the VUV region. It could be considered that this band was composed of two bands at about 160 and 166 nm. The preceding band was assigned to the BO 3 group absorption. The later one at about 166 nm could be assigned to the charge transfer (CT) transition of Gd 3+–O 2−. Such an assignment was deduced from the result that broadbands at around 170 nm for GdAlO 3:Eu, and at 183 nm for Gd 2SiO 5:Eu are due to the CT transition of Gd 3+–O 2−; this was also identified by CaZr (BO 3) 2:Eu. Since there are no Gd 3+ ions in it; a weak band in the VUV region in the excitation spectrum of Ca 0.95ZrEu 0.05(BO 3) 2 was observed. The excitation spectra were overlapped between the CT transition of Gd 3+–O 2− and BO 3 group absorption, and it caused the emission of Eu 3+ effectively in the trivalent europium-doped (Gd,Y)BO 3 host lattice under 147 nm excitation. Intense broad excitation bands were observed at about 155 nm for YBO 3:Eu and at about 153 nm for YAlO 3:Eu; it could be attributed to the CT transition between Y 3+ and O 2−. As a result, under the xenon discharge (147 nm) excitation, the intense emission of Eu 3+ in GdBO 3 was found to be more convenient just because of the partial substitution of Y 3+ for Gd 3+.