摘要:
本文采用高温固相反应法制备了Ba5SiO4Cl6： Yb3+， Er3+， Li+荧光粉，并对其上转换发光性质及其发光机理进行了研究.在980 nm激光的激发下， Ba5SiO4Cl6： Yb3+， Er3+荧光粉呈现较强的红色(662 nm)和较弱的绿色(550 nm)的上转换发光，红色和绿色的上转换发光分别对应于Er3+离子的4S3/2/2H11/2→4I15/2和4F9/2→4I15/2跃迁，且随着掺杂的Er3+和Yb3+离子浓度增加，样品的上转换发光强度增加，这是因为Yb3+离子和Er3+离子之间的能量传递效率增加引起的.在0.5—0.8 W功率激发下，样品属于双光子发射，而在0.9—1.2 W功率激发下样品具有新的上转换发光机理--光子雪崩效应.探讨了Li+掺杂对Ba5SiO4Cl6： Yb3+， Er3+样品的上转换发光性质的影响， Li+离子的掺杂引起Ba5SiO4Cl6：Yb3+， Er3+上转换发光强度增加，这是由于Li+离子的掺入降低了晶体场的对称性引起的。
Abstract:
The Ba5SiO4Cl6: Yb3+, Er3+, Li+ phosphor has been prepared by high temperature solid state reaction, and their upconversion (UC) luminescence properties and mechanisms are investigated. The UC emission bands located at 525 nm (2H11/2→4I15/2), 548 nm (4S3/2→4I15/2), and 662 nm (4F9/2→4I15/2) due to Er3+are observed under the excitation of 980 nm. UC luminescence of Ba5SiO4Cl6: Yb3+, Er3+ phosphors is increased with increasing Er3+ and Yb3+ concentration due to the energy transfer enhancement of Er3+ and Yb3+. Based on the relations of UC luminescence intensity and excitation light power, the UC luminescence mechanisms are discussed. At a low excited power (below 0.8 W), the two-photon processes are involved in both green and red UC emission mechanisms. When the power exceeds 0.9 W, the green and red UC emission is a four-photon process. One new and interesting UC emission mechanism may occur in the Ba5SiO4Cl6: Yb3+, Er3+ phosphors. Both green and red UC emissions at a higher pumping power are generated by photon avalanche UC process. Influence of Li+ doping on the UC luminescence of Ba5SiO4Cl6: Yb3+, Er3+ phosphors is investigated. Result demonstrates that Li+ ion doping could enhance the UC luminescence of Ba5SiO4Cl6: Yb3+, Er3+, which is attributed to the distortion of the local symmetry around Er3+.
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