Preparation Of SrAl₂O₄: Eu～(2+), Dy～(3+) Phosphor And The Effect Of Boron Substitution

Eu2+ and Dy3+ co-activated monoclinic SrAl2O4 phosphors were prepared by coated-precipitation method. Based on that, the effects of Boron substitution on the phosphor have been studied. Besides, detailed parameters of the coated-precipitation were investigated; chemical and physical processes brought by Boron substitution were discussed in this paper.The Sr2+and rare earth ions were deposited on Al(OH)3 substrate by H2C2O4 as precipitator at pH value 7 around and at 40℃-45℃. After filtering, washing, and drying, the deposit-substrate precursor was obtained, which calcined in weak reductive atmosphere can form the SrAl₂O₄:Eu²⁺,Dy³⁺ phosphor. The ratio of the precipitation of Sr2+ was investigated by ICP, the processes of heat treatment were studied by the TG-DTA and XRD, the particle morphology and grain size of the powders were inspected by SEM. Excitation and emission spectra and decay characteristic of afterglow of the phosphor were investigated. The results show that SrAl₂O₄:Eu²⁺,Dy³⁺ phosphor can be synthesized at 1200℃, lower than traditional solid-state reaction, products have fine luminescent properties.Boron substitution mainly affects the calcination process of the precursor. Melted at about 450℃, boron oxide provides the precursor some liquid phase,which can sharply improve particle diffusion and transfer, and accelerate the synthesis of SrAl2O4. When cooling-down, most of liquid boron oxide turns into glass phase and stays beyond the lattice. Besides, tiny amounts of boron enter the SrAl2O4 crystalline lattice in the form of [AlO4] tetrahedron; markedly increase phosphor's brightness and durative time by affecting the activated center and Dy3+ trap, the substitutive boron may also forms a new category of energy trap independently. For example, the afterglow brightness at the 10th second of SrAl₂O₄:Eu²⁺,Dy³⁺ with 10% boron is as 3 times as that of SrAl₂O₄:Eu²⁺,Dy³⁺ without boron; the former's brightness at the 30th minute is even more greater than the latter's. Boron substitution also makes phosphor powders conglutinate and hard to suspended, which are harmful to its application. Besides, the"Blue-shift"of phosphor's emission peak is observed as the content of boron increased.