Research On The Blue Long Afterglow Phosphorescent Material Sr₂MgSi₂O₇:Eu～(2+), Dy～(3+) Fabricated From Combustion Synthesis

Silicate-based long afterglow phosphorescent materials relatively complement the aluminate system in luminescent color, and perform well when excited with ultraviolet light. Moreover, they are stabile in wet,hot or chemical erosion circumstance .So, they have been attracting more attention in recent years.Mesosilicate grains were well crystallized by combustion synthesis in this dissertation. The grain size was nearly 21nm. The analytical results indicated that the samples prepared by this method displayed strong luminescence intensity. At the same time,We evaluated the influence factors on luminescence of phosphor ,found out the best combustion synthesis condition of Sr2MgSi2O7: Eu2+,Dy3+.The best combustion synthesis condition was listed as follows: The temperature of muffle was 650℃,H3BO3 / Mg(NO3)2 (molar ratio) was 0.175:1, carbamide/nitrate(quality ratio) was 2.5:1,Eu2+ / Mg(NO3)2 (molar ratio) was 0.035:1 and Dy3+ / Eu2+ (molar ratio) was 1:1.The optical properties of the sample were characterized by spectrophotofluorometer.Its excitation spectra were continuous bands, centered sharply at 352nm and the excitation showed broadband absorptions from ultraviolet to visible light. The emission spectra were broad bands, centered sharply at 468nm due to the 4f—5d transition of the Eu2+ ion. No other special emission peaks of Eu3+ are observed in the spectra, which proves that Eu3+ in the matrix crystals have been reduced to Eu2+ completely.The obtained phosphor was characterized by means of X-ray diffraction (XRD),the result indicated that the Sr2MgSi2O7 phase had formed in the synthesis process. The doping ions, Eu2+,Dy3+ did not destroy the crystal structure of Sr2MgSi2O7,but occupied the octa-coordinated Sr 2+ sites in the Sr2MgSi2O7 host. Sr2MgSi2O7 was a mesosilicate with akermanite structure ,which belonged to pyramidal system.According to the d-I data of the XRD patterns of Sr2MgSi2O7: Eu2+,Dy3,we calculated the cell parameters of its .The two important cell parameters were a=7.95A and c=5.09A.We studied the influence of different silica and magnesium materials on luminescence of phosphor and that of different doping ions. The result indicated that not only the purity of silica materials was important to luminescence of phosphor but also the finestiny, magnesium materials were not so important only when they were A.R. degree. Doping of Gd3+ helped to enhance the long-lasting phosphorescence of phosphor . Gd3+ -doped Sr2MgSi2O7 had evidently higher brightness than Sr2MgSi2O7: Eu2+,Dy3+,exactly when the Gd3+ / Dy3+ (molar...