Optical properties of Tb3+-doped Rb2KInF6 elpasolite

Crystals of Rb2KInF6:Tb3+ with elpasolite structure have been prepared by t he Bridgman method. Absorption, wide range luminescence, high resolution em ission, excitation and luminescence decay measurements have been carried ou t at low and room temperature in order to study the environments of Tb3+ io ns and their optical properties. An O-h Site of Tb3+ ions (octahedral TbF63 -; units) has been found and the identification and assignment of the pure magnetic-dipole transitions split out of the Tb3+ D-5(4) --> F-7(6), F-7(5) , F-7(4), F-7(3) and D-5(3) --> F-7(6), F-7(5), F-7(4) transitions have bee n achieved assuming a thermal equilibrated set of crystal-held sublevels an d comparing with the literature data in chloride and fluoride elpasolites; a C-2v distortion of the octahedral symmetry has been detected at low tempe rature. Some experimental results could suggest the presence of a small con centration of other sites of Tb3+ with a symmetry lower than Oh. Energy tra nsfer between the two sites could also be suggested. Finally, an up-convers ion process by means of sequential two-photon absorption (F-7(6) --> D-5(4) and D-5(4) --> above D-5(3)) has been demonstrated. (C) 1999 Elsevier Scie nce B.V. All rights reserved.