Optical properties of Mn2+ in KCaF3 single crystal

It is known that the spectroscopic properties of 3d impurities in crystals are very sensitive to the environment of the ion and can be changed considerably by using different matrices. The crystal structure of KCaF3 has been previously determined by the Rietveld profile method. At room temperature, KCa1-xMnxF3 (x < 0.1) crystallizes in monoclinic C-2h (B2(1)/m) symmetry. The local geometries around Mn2+ in this crystals, in their ground and excited states, are the primary properties that govern the spectroscopic behavior of these systems, which enjoy of fundamental and technological interest. The present work reports the absorption and luminescence spectra of the Mn2+-doped KCaF3 (fluoroperovskite). The luminescence spectra recorded over a range of temperatures are dominated by wide bands, corresponding to the T-4(1)(G) --> (6)A(1)(G), Mn2+ transition. The lifetime (tau = f(T)) of the first excited state T-4(1)(G) was measured as a function of temperature. The lifetime of the Mn2+ emission, in this crystal have been found to be temperature independent (tau < 7 mu s). The absorption and emission spectra of Mn2+ (3d(5)) in KCaF3 are analyzed using a C-4 crystal-field hamiltonian. The calculated energy levels are in good agreement with those obtained experimentally. The resulting crystal-field parameters B-nm are a good representation of the crystal-field interactions of Mn2+ in KCaF3. (C) 1999 Elsevier Science B.V. All rights reserved.