Gd_2O_3∶(Ce^(3+),Eu^(3+))微晶中稀土离子间的级联能量传递

Cascade Energy Transfer in Gd_2O_3∶(Ce^(3+),Eu^(3+)) Micro-crystal

本文报道了纳米Gd2 O3∶(Ce3+ ,Eu3 + )的紫外与真空紫外 (UV VUV)激发谱及其选择激发下的荧光光谱。这些光谱实验表明 ,除了Gd2 O3 基质与Ce3+ ,Eu3 + 离子之间的能量传递外 ,还存在着Gd3+ 与Ce3 + 、Eu3 +间的能量传递 ,即存在Gd3+ →Ce3+ →Eu3 +

Gd 2O 3∶(Ce 3+ , Eu 3+ ) is a potential luminescent material which can act both in fundamental research and application. In the past two years, Wegh et al . realized the quantum cutting grounded on the energy transfer between some rare earth ions such as Gd 3+ →Eu 3+ , Gd 3+ →Er 3+ and so on, the quantum efficiency approximates to 200%. So we investigated the energy transfer in Gd 3+ Ce 3+ Eu 3+ system, prepared for the design of the new type materials based on effective quantum cutting. Gd 2O 3∶(Ce 3+ , Eu 3+ ) micro crystals were prepared by the sol gel method. The samples were checked to be pure cubic phase by X ray powder diffraction, the mean size of particles is about 400nm. The excitation spectra of Ce 3+ ( λ em =450nm) and Eu 3+ ( λ em =619nm) in the UV range were researched, and the emission spectra of Ce 3+ and Eu 3+ were measured with UV excitation respectively. The results showed that the energy transfer between Gd 3+ and Ce 3+ , Gd 3+ and Eu 3+ , Ce 3+ and Eu 3+ correspond to the energy transfer from 8S 7/2 → 6D J and 8S 7/2 → 6I J (Gd 3+ ) to 4f ( 2F 7/2 , 2F 5/2 )→5d (Ce 3+ ), from 8S 7/2 → 6D J and 8S 7/2 → 6I J (Gd 3+ ) to 7F 1,2,3,4 → 5D 0 (Eu 3+ ), and from 5d→4f( 2F 7/2 , 2F 5/2 ) (Ce 3+ ) to 7F 1,2,3,4 → 5D 0 (Eu 3+ ),respectively. We also made use of synchrotron radiation light to detect the excitation spectra of Gd 2O 3∶(Ce 3+ , Eu 3+ ) in the UV VUV range, and the emission spectra with VUV (180nm) excitation. The emission spectra of Ce 3+ ( λ em =450nm) was decomposed to four sub bands with UV excitation, while it was decomposed to two sub bands under VUV excitation. These results indicate that Ce 3+ substituted for Gd 3+ and located in two kinds of different sub lattices. Gd 3+ can transfer energy to two kinds of different sub lattices effectively, while the host just can transfer energy to one kind of different sub lattices. The energy transfer from 8S 7/2 → 6D J and 8S 7/2 → 6I J (Gd 3+ ) to 4f ( 2F 7/2 , 2F 5/2 )→5d (Ce 3+ ), and from 5d→4f( 2F 7/2 , 2F 5/2 ) (Ce 3+ ) to 7F 1,2,3,4 → 5D 0 (Eu 3+ ) occurred simultaneously, so it is concluded that the cascade energy transfer Gd 3+ →Ce 3+ →Eu 3+ exists in Gd 2O 3∶(Ce 3+ , Eu 3+ ) micro crystals .