白光LED用橙红色荧光体Sr_2MgSi_3O_9:Eu~(3+)的制备和光谱性质

采用凝胶-燃烧法在活性炭弱还原气氛下成功合成了新型橙红色发光材料Sr2MgSi3O9:Eu3+.用X射线粉末衍射仪(XRD)、扫描电镜(SEM)、荧光分光光度计等对合成产物进行了分析和表征.结果表明:此发光材料与Sr2MgSi2O7具有相似的晶体结构,同属四方晶系.样品的一次颗粒近似球形,粒径在100 nm左右.样品Sr2MgSi3O9:Eu3+的激发光谱在220~300 nm内出现一宽带吸收,归属于Eu3+-O2-之间的电荷迁移带,300 nm以后出现的锐线峰为Eu3+的f→f跃迁吸收峰,其最强锐线峰位于400 nm,对应于Eu3+的基态到5L6激发态跃迁吸收,因而,可以被InGaN管芯产生的紫外辐射有效激发.发射光谱由2个强发射峰组成,位于592 nm和618 nm处,分别属于典型的Eu3+的5D0→7F1和5D0→7F2跃迁.此外,研究还发现共掺杂适量Ti使得发光颜色由橙红色向红色转变,发光强度明显增强.

Preparation of Orange-red Emitting Phosphors Sr_2MgSi_3O_9:Eu~(3+) for White LEDs and Its Photoluminescent Properties

Novel phosphors Sr_2MgSi_3O_9:Eu~(3+) synthesized by gel-combustion method in weak reductive environment.The as-synthesized phosphors were investigated by XRD, SEM and Fluorescence spectrophotometer. The results show that Sr_2MgSi_3O_9: Eu~(3+) phosphor possesses the similar tetragonal crystal structure as that of Sr_2MgSi_2O_7. The initial particles of as-synthesized phosphors are nearly spherical in shape, and the particle size is about 100 nm in diameter. The excitation spectrum of Sr_2MgSi_3O_9:Eu~(3+) sample presents wide band absorption between 220～300 nm, which is ascribed to the charge transfer between Eu~(3+)-O~(2-). The sharp peaks after 300 nm belong to f→f transition of Eu~(3+), and the strongest sharp peak is located at 400 nm, which is ascribed to the transition from the ground state of Eu~(3+) to ~5L_6 excited state. Therefore, samples can be efficiently excited by ultraviolet radiation from InGaN chip. The emission spectrum consists of two emission peaks at 592 nm and 618 nm, which are ascribed to ~5D_0→~7F_1 and ~5D_0→~7F_2 respectively. Moreover, it is found that co-doped Ti~(4+) with the proper content can make the emitting colour shift from orange-red to red, and improve intensity of luminescence effectively.