Abstract

The M₂MgSi₂O₇: Eu²⁺, Dy³⁺ (M: Sr, Ca) long afterglow phosphors are investigated by substituting the Ho³⁺ ions for the Dy³⁺ ions. The emission intensity is about 3 times and 30% enhanced with this substitution in the Sr₂MgSi₂O₇ and Ca₂MgSi₂O₇ host, respectively. The emissions of the europium ions and the holmium ions are observed. Both emissions attribute to the 5d → 4f transition, indicating that some of the Ho³⁺ ions are reduced to the Ho²⁺ ions. The Ho³⁺ ions or the Dy³⁺ ions aggregate with the cation and the oxygen vacancies forming the traps. The traps induced by the clusters with Ho³⁺ ions are shallower than those induced by the clusters with Dy³⁺ ions. The traps’ concentration of the Ho³⁺ cluster is lower. The probability of retrapping of the released carriers decreases with the Ho³⁺ ions co-doping. The combination effect of the shallow traps and the non-retrapping process gives rise to a greater intensity of the initial emission and a shorter duration of the afterglow.