The VUV luminescence properties and the Ce³⁺ → Tb³⁺ energy transfer in the (Sr, Ba) Al₁₂O₁₉

The (Sr, Ba) Al₁₂O₁₉:RE³⁺ (RE = Ce, Tb) compounds have been synthesized by the solid state reaction technology. The single-phase magnetoplumbite-type crystal structure has been identified by the X-ray diffraction analysis. The 302 nm peak and -340 nm not-clear shoulder are correspondence to the 5d → ²F_5/2 and 5d → ²F_7/2 transitions in the emission spectrum, respectively. The 158 nm peak and 260 nm peak are separately contributed to the host absorption and 4f-5d transition of Ce³⁺ in the excitation spectrum. The characteristic emission of ⁵D₃ → ⁷F_j (j = 2, 3, 4, 5) and 5D₄ → ⁷F_j (j = 4, 5, 6) transitions in the range of 400-600 nm are assigned in the emission spectrum of (Sr, Ba) Al₁₂O₁₉:Tb_0.05³⁺. The -160 nm peaks arises from the overlap of the Tb³⁺-O^2- charge transfer band and the host absorption. The 193 nm and 233 nm peaks are attributed by the spin-allowed 4f-5d transition and the spin-forbidden transition, respectively. The overlap between the emission of Ce³⁺ and the f-f transition absorption of Tb³⁺ exists in the (Sr, Ba) Al₁₂O₁₉:Tb³⁺, Ce³⁺ compounds. The luminescence intensity of Tb³⁺ increases with the increase of the Ce³⁺ ion concentration. When the Ce³⁺ ion concentration reaches about 0.03 mole, the luminescence intensity of Tb³⁺ ion is nearly two times comparing with the non-codoping Ce³⁺ ion compounds. When the emission wavelength is 543 nm, the excitation spectra exhibit the 4f-5d absorption of Ce³⁺ besides the host absorption and 4f-5d transitions of Tb³⁺ in the (Sr, Ba) Al₁₂O₁₉:Tb³⁺, Ce³⁺ compounds. According to the excitation spectrum, the part of the emission of Tb³⁺ comes from the absorption of Ce³⁺ ion. Therefore, it is illustrated that the Ce³⁺ → Tb³⁺ energy transfer has been existed in the (Sr, Ba) Al₁₂O₁₉:RE³⁺ (RE = Ce, Tb) compounds.