水热法合成YLiF_4∶Er^(3+)的上转换发光

Upconversion Luminescence of YLiF_4∶Er^(3+) Synthesized by Hydrothermal Method

用水热法合成了YLiF4∶Er3+,Er3+浓度变化范围为0%~5%。在室温下,测试了所有样品在200~1200nm间的吸收光谱。当Er3+浓度为2%(Er-2样品)时,由吸收光谱计算得到的J-O参数为Ω2=1.05×10-20cm2,Ω4=1.25×10-20cm2和Ω6=1.35×10-20cm2。在980nm激发下,测试了所有样品的上转换发光光谱,发光强度随Er3+浓度增加而增长。当Er3+浓度小于1.5%,激发态吸收是主要的上转换发光机制。当Er3+浓度高于1.5%时,上转换机制包括激发态吸收和能量传递。在室温下,Er-2样品的能级2H11/2的寿命是205μs,4S3/2的是205μs,4F9/2是188μs。根据实验数据和计算所得的跃迁几率,计算了4S3/2能级和4F9/2能级的量子效率,分别是27.9%和10.7%,表明两者都具有很高的量子效率。

YLiF4：Er^3＋ was synthesized by hydrothermal method. Concentration of Er^3 ＋ is changed from 0 to 5 %. The absorption of Er^3＋ in all samples from 200 to 1200 nm was measured at room temperature. The J- O parameters calculated from absorption spectrum areΩ2=1.05×10^-20 cm^2,Ω4=1.25×10^-20 cm^2 and Ω6=1.35×10^-20 cm^2. Infrared-to-visible upconversion emission of YLiF4：Er^3＋ was observed when excited at 980 nm. The results show that the Er^3 ＋ content is less than 1.5%, excite-state absorption is the main mechanism of upconversion emission. When Er^3 ＋ content is larger than 1.5 %, both of the excite-state absorption and energy transfer lead to the upconversion luminescence. The upconversion intensity is enhanced with the increasing of Er^3＋ concentration. At room temperature, the lifetime of ^2H（11/2） and ^4S（3/2） is 205 μs while that of ^4F（9/2） is 188μs for sample Er-2. The transition rates and quantum efficiency were also calculated. The quantum efficiencies of ^4S（3/2） and ^4F（9/2） are 27.9% and 10.7%, respectively.