Eu2+和Dy3+掺杂浓度对Sr2MgSi2O7材料的荧光和长余辉性能的影响

采用高温固相法制备得到Sr₂MgSi₂O₇: Eu²⁺和Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺发光粉, 并详细研究了Eu²⁺和Dy³⁺的掺杂浓度对Sr₂MgSi₂O₇材料的荧光和长余辉性能的影响。所有样品都在470 nm附近呈现较宽的发光峰, 这可归因于Eu²⁺离子的4f⁶5d→4f⁷电子能级跃迁。当Eu²⁺掺杂浓度超过淬灭浓度, 其浓度淬灭效应导致发光粉的荧光强度下降和余辉时间减短。同时, 发射峰的峰位随Eu²⁺浓度的增加而发生红移, 这主要由于晶体场分裂能和斯托克斯位移变化造成的, 而电子云扩大效应变化所产生的影响相对较弱。Dy³⁺离子会抑制荧光, 但有助于延长余辉时间。当其掺杂浓度超过10mol%时, Eu²⁺\Dy³⁺离子通过隧道复合机制发生浓度淬灭, 从而使材料的长余辉寿命减少。

Influence of Eu2+ and Dy3+ Concentrations on Fluorescence and Phosphorescence of Sr2MgSi2O7 Phosphors

Eu²⁺-doped Sr₂MgSi₂O₇ and Eu²⁺ and Dy³⁺ codoped Sr₂MgSi₂O₇ phosphors were synthesized by conventional solid-state reaction. Eu²⁺ and Dy³⁺ concentration effects on the fluorescence and phosphorescence of Sr₂MgSi₂O₇ phosphors were studied. All the samples show a broad emission band centered at about 470 nm, which are ascribed to 4f⁶5d→4f⁷ transition of Eu²⁺ ions. Concentration quenching is found to be the dominant factor decreasing emission intensity and afterglow duration time when Eu²⁺ doping level exceeds the critical concentration. Redshift of the emission bands is also observed as the Eu²⁺ concentration increasing. In order to explain the redshift of the emission bands, the centroid position of 5d level of Eu²⁺, crystal-field splitting energy and Stokes shift are estimated from excitation and emission spectra. Based on the calculation, the redshift of the emission bands mainly results from the variations of crystal-field splitting energy and Stokes shift, but is less influenced by the nephelauxetic effect. The Dy³⁺ ions suppress the fluorescence but enhance the phosphorescence lifetime. When the Dy³⁺ concentration is over 10mol%, the phosphorescence lifetime is shortened, because of concentration quenching of the Eu²⁺\Dy³⁺ ions by the mechanism of tunneling recombination.