Localization of Eu3+ in KGd1 9Eu0.1F7 and KGd1.9Eu0.1F6.97O0.015 by site-selective excitation and time-resolved spectroscopy

Abstract This paper reports site-selective excitation (or observation) and time-resolved spectroscopy of the host matrices KGd 2 F 7 and KGd 2 F 6.97 O 0.015 doped by Eu 3+ . The crystal structure of KGd 2 F 7 derives from that of the fluorite-type, by an ordering of the cations and anions. The luminescence spectra and site-selective excitation in the 5 D 0 → 7 F 0 region, have allowed to identify several distributions of discrete sites for the Eu 3+ ions, in which two sites are characterized by unusual spectra which are attributed to Eu–O bonds. Another kind of site, characteristic of fluorinated surroundings close to the centrosymmetry, exhibits a very long lifetime (6.8 ms) of the 5 D 0 level. Although the accurate structures of these compounds are not yet known, they are very close to that of KGd 2.77 F 9.32 previously solved and the spectroscopic results are in agreement with the number and the symmetries of the rare earth crystallographic sites.