Sr_(1-x)Ba_xAl_2O_4∶Eu^(2+),Dy^(3+)磷光体的制备及其发光特性

Preparation and Luminescence Properties of Sr_(1-x)Ba_xAl_2O_4∶Eu^(2+),Dy^(3+)

采用高温固相法在1350℃弱还原气氛下制备了Sr1-xBaxAl2O4∶Eu2+,Dy3+(x=0,0.2,0.4,0.6,0.8,1.0)长余辉材料,并对其微观结构和发光特性进行了分析。X射线衍射结果表明,当钡的掺杂摩尔分数x<0.4时,样品晶体结构为SrAl2O4单斜晶系结构;当x≥0.4时,样品晶体结构为BaAl2O4六角晶系结构;而且随着钡对锶的取代,两种晶体结构的晶格常数都发生了一定程度的膨胀。光致发光测试结果表明,当x从0增大到1.0时,样品发射波长峰值也相应由515nm逐渐蓝移到494nm。通过热释光谱测试表明,SrAl2O4结构的样品的热释光峰所对应的温度比BaAl2O4结构的要高,且对应SrAl2O4结构的样品的余辉时间更长,初始亮度更高。

The long afterglow photoluminescence materials have the particular＂ properties storing light energy and glowing slowly at dark circumstances. That is, the materials can absorb the visible lights, store the energy, and then release the energy as the visible lights. Particularly, alkaline earth aluminates doped with rare earth ions have excellent luminescence properties such as high brightness, no radiation, safety, long duration, and environmental capability, resulting in its wide applications in many fields. In this paper, Sr1-xBaxAl2O4＂ Eu^2＋ Dy^3＋（ x = 0,0.2,0.4,0.6,0.8,1.0） phosphors were synthesized in a reducing atmosphere by high temperature solid state method at 1 350 ℃with H3BO3 as flux. The phosphors were characterized by X-ray diffraction （XRD）. The results showed that crystal structure of the phosphors is the monoclinic phase of SrAl2O4 when x 〈0.4 and the hexagonal phase of the BaAl2O4 when x≥ 0.4. The lattice plane distances of the phosphors increase with the content of Ba^2＋ , which could be explained that Ba^2＋ ion radius is bigger than that of Sr^2＋ ion. The crystal lattice expands with barium ion substitution for strontium ion. Photoluminescence experiments were carried out to study luminescence properties of the phosphors under the excitation of UV. The results showed that the peak of the emission spectra shifts from 515 nm to 494 nm with the x changing from 0 to 1. 0. The blue shift phenomenon could be explained by the crystal field effect, which is affected by different coulomb attractive forces due to Ba^2 ＋ ion doping in the host lattice. Long afterglow properties were investigated by thermoluminescence. Thermoluminescence measurements showed that trap energy level of the SrAl2O4 crystal structure is deeper than that of BaAl2O4. The afterglow decay showed that the phosphors of SrAlO4 crystal structure have the more superior afterglow performance of BaAl2O4.