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Long afterglow Sr₂MgSi₂O₇ (SMS) phosphor was prepared by Douby's methods at high temperature and reductive atmosphere. The excitation and emission spectra of this phosphor showed that both had broad bands and that the main emission peak at 469 nm was due to 4f‐5d transitions of Eu⁺² and implied that the luminescence centres Eu⁺² occupied the Sr⁺² sites in the Sr₂MgSi₂O₇ host. The phosphor doped only with Eu ions did not demonstrate the long afterglow phenomenon, but when co‐doped with Dy⁺³ ions in the SMS matrix, significant long afterglow was observed.

The purpose of this paper is to investigate the effect of boric acid as a flux on the formation of the akermanite phase and optical properties of SrMgSi₂O₇:Eu,Dy phosphors.

The silicate‐based phosphor is prepared by sol‐gel method. Sr(NO₃)₂, Mg(NO₃)₂ · 6H₂O, Dy₂O₃, Eu₂O₃, are added to distilled water in their stoichiometric ratio, the obtained solution are mixed with H₃BO₃ (in the range of 0.01‐0.5 mol%) and a polymeric compound TESO (C₈H₂O₄Si). At the end, the phase composition and optical properties are investigated using X‐ray diffraction (XRD) and spectrophotometer analysis, respectively.

The XRD results showed that the akermanite (Sr₂MgSi₂O₇) is the only crystalline phase which is detected in the sample containing 0.05 mol% boric acid. Increasing of boric acid does not have a great effect on the XRD patterns intensity. Spectrophotometer analysis results show three maximum at 365, 395 and 430 nm on the excitation spectra. It also shows intensity of the excitation and emission spectra increased by adding boric acid up to 0.25 mol% and a sudden drop at 0.5 mol% boric acid.

Using boric acid as a flux, enhances formation of akermanite phase at lower temperature with desirable optical properties and a cost‐benefit way for industrial production. In this research, optimum value of boric acid was determined using XRD data, emission and excitation spectra.