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 (CeI, CeII, CeIII, 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 CeIII center which luminescence is slightly quenched by Yb2+.