ARF4(A=Na,K;R=La,Gd,Y,Lu)中Eu2+的光谱结构及其价态稳定性

Eu2+在ARF4(A=Na,K;R=La,Gd,Y,Lu)中的荧光光谱结构是由特征的d→f跃迁宽带发射和f→f跃迁尖峰发射组成,低温下线/带强度比明显增强;高纯氩气流中合成的样品,Eu2+的价态是稳定的。

SPECTRAL STRUCTURE AND VALENCE STABILITY OF EUROPIUM (Ⅱ) IN SYSTEMS ARF4 (A=Na,K; R=La,Gd,Lu and Y)

A study was made on the spectral structure characterization and valence stability of Eu2+ ions in ARF4 (A=Na, K; R=La,Gd,Lu and Y), one of complex fluorides useful as multifunctional materials.Alkali metal ions have the lowest ionizing potential and highest positive electricity and stronger ionic bond is formed easily in its compounds.The Eu2+ ion probably is given priority to occupy a alkali ionic lattice site in the complex fluorides synthesized by alkali and rare earth fluorides because the alkali ions have smaller electronegative and longer ionic radius than Eu2+ ion.Systemic compounds of this complex fluorides were synthesized with successive firing in a stream of high purity argon (0.51/min) in the temperature range of 550-800C. However, compounds of systems AF-Rf3 (A=Rb, Cs;R=La,Gd,Lu and Y) were not obtained.A sharp peak at 360 nm was observed in the fluorescence emission structure of Eu2+-doped ARF4, when R=Gd,Lu or Y at 300K, or R=La at 77K. The emission arises from 4f7 (6P7/2)-4f7 (8S7/2) transition of Eu2+ ions. In addition to sharp peak emission, broad band was observed at 396nm. In concordance with criterion of electronic transition of Eu2+ ion in complex fluorides, both d-f and f-f transitions could be observed, with the energy difference between absorption bottom of 4f-5d and centre of gravity for 6P7/2 being smaller than 300cm-1. No sharp peak emission of Eu2+ ion was observed in systems AR’F4 (A=Na, K; R''=Lanthanoid ions except La, Gd and Lu).The data on ESCA and magnetic susceptibility show that divalence europium is stable in ARF4:Eu2+ synthesized in the stream of high purity argon.