ZnS∶Zn,Pb宽带蓝色发光和发光机制

Mechanism of Blue Emission Band Phosphors ZnS∶Zn,Pb

用固相反应法制备了一系列ZnS∶Zn,Pb荧光粉。改变不同的灼烧温度和激活剂的掺杂量,通过对灼烧后荧光粉进行光谱分析,我们发现Pb2+在ZnS基质中的发光与制备条件有关:灼烧温度为800～950℃时,能得到Pb2+在ZnS基质中的蓝色发光。测量了其光致发射光谱、激发光谱,以及灼烧后荧光粉的成分。研究了阴极射线下ZnS∶Zn,Pb荧光粉的相对发光亮度与荧光粉电压的关系,ZnS∶Zn,Pb的相对亮度比ZnS∶Ag,Cl的高,比ZnS∶Zn更高。研究了发光衰减时间与温度的关系,得到了ZnS∶Zn,Pb的蓝色发光可能来源于Pb2+的D波段发射的结论。并对其发光机制进行了一些探讨。这种新型蓝粉可应用于VFD和FED等低压显示屏。

Zinc sulfide phosphors are currently of interest for use in a wide range of application including CRT and FED applications. In the engineering of phosphors for low voltage operation, the stoichiometry and composition must be studied and controlled so that the desired objectives of improved powder phosphors can be achieved. This will lead to a better understanding of the processes taking place. The Pb2+ ion belongs to ns2- type impurities. When Pb2+ was added into ZnS, its emissions are probably observed,including blue, green and red emission band. The luminescence properties of ZnS∶Zn,Pb was strongly dependent on the preparation conditions. In this paper the luminescence of ZnS∶Zn, Pb was studied. The influence of the firing temperature and the Pb2+ concentration used in the synthesis on the origin of the blue luminescence was discussed. After the raw materials was fried at about 950℃ for an hour, the blue luminescence phosphors ZnS∶Zn,Pb was obtained. It was shown that ZnS∶Zn,Pb gives rather efficient blue emission under low excitation voltages. The brightness of ZnS∶Zn,Pb is higher than that of ZnS∶Ag,Cl and ZnS∶Zn. To explain the origin of the blue emission, the lifetime measurements were performed. A strong decrease of the luminescent lifetime from ms to μs with increasing temperatures was typically found. In view of the similarity in the lifetime behaviour for Aband and Dband emission from Pb2+, the lifetime experiments did not provide evidence for either Aband or Dband emission from Pb2+. It is possible to distinguish between defect related ZnS emission (μs) and Pb2+ related emission bands. For Pb2+ emission band (Aband or Dband) a long lifetime (ms) at low temperatures decreases to μs between ～50K and 150K. It is known that the red emission band was related to the Aband, so the blue emission band was probably related to the Dband. That is mean the Dband emission of Pb2+ in ZnS close to a defect (e. g. S2- vacancy or O2- on S2-site). 