Intervalence charge transfer in Pr 3+- and Tb 3+-doped double tungstate crystals KRE(WO 4) 2 (RE = Y, Gd, Yb, Lu)

Abstract

First experimental evidences of intervalence charge transfer (IVCT) transitions in Pr 3+- and Tb 3+-doped double tungstate crystals KRE(WO 4) 2 (RE = Y, Gd, Yb, Lu) are reported. The IVCT bands are located nearly at the same energies for Pr 3+ and Tb 3+ in a given crystal and these energies are consistent with an empirical model recently developed for Pr 3+ ions in titanates, vanadates, niobates and tantalates. These data made it possible to locate the 4f n states of trivalent lanthanides in KREW crystals by applying the “double seat” empirical model proposed by Dorenbos.