Spectral-kinetic studies of SrAlF5 doped by trivalent rare-earth ions

Photochemical properties of Ce³⁺:SrAlF₅ and Ce³⁺,Yb³⁺:SrAlF₅ single crystals together with spectroscopic and kinetic characteristics of several optically nonequivalent impurity centers and energy transfer between them are described. It is shown that co-activation by Yb³⁺ ions effectively suppresses color centers in Ce,Yb:SAF crystals. It was found out that in Ce,Yb:SAF crystals Yb ions exist simultaneously in 2+ and 3+ valent state. Three types of optically nonequivalent luminescent centers corresponding to the doublets in luminescence spectrum centered at 290, 305 and 370 nm (Ce^I, Ce^II, Ce^III, respectively) have been observed. Analysis of luminescence spectra and decays leads to the conclusion that there is no energy transfer between either cerium centers or from Ce³⁺ to Yb²⁺ apart from the Ce^III center which luminescence is slightly quenched by Yb²⁺.