Infrared spectra and luminescence properties of (Y_x,Gd_0.95-x)BO₃:Eu_0.05³⁺

The luminescence compound (Y_x,Gd_0.95-x)BO₃:Eu_0.05³⁺ with a single phase hexagonal crystal structure has been synthesized by the solid state reaction. The c/a value is linearly decreasing when the ratio of Y³⁺/Gd³⁺ is increasing, which indicates that the solid-solution of YBO₃ and GdBO₃ is forming. The two symmetric stretching vibration peaks of the BO₄ anion at 866 and 912 cm^-1 in the FTIR spectrum exist in two forms in the solid solutions. The local symmetric environment surrounding the Eu³⁺ ion was lowered with the decrease of Y³⁺/Gd³⁺ ratio. The host absorption band and Eu³⁺-O^2- charge transfer band were observed in the excitation spectra of (Y_x,Gd_0.95-x)BO₃:Eu_0.05³⁺. In particular, the relative intensity of Eu³⁺-O^2- charge transfer band sharply decreased when the ratio of Y³⁺/Gd³⁺ increased was identified by the variation of local symmetric environment around Eu³⁺. The ratio of the fluorescence intensity of ⁵D₀ → ⁷F₂ transition and ⁵D₀ → ⁷F₁ transition (R/O ratio) is decreasing with the increasing of Y³⁺ content.