Optical spectra of a LaGaO3 crystal singly doped with chromium, vanadium and cobalt

Crystals of lanthanum orthogallate containing chromium, vanadium or cobalt were grown by the Czochralski method and their optical spectra were measure d at room and 5K temperature. Recorded absorption and luminescence spectra of chromium ions which are convenient probes of number and type of availabl e sites revealed that Cr3+ ions in LaGaO3 occupy identical sites with disto rted octahedral symmetry and consistent with a strong crystal field case. A bsorption spectra of vanadium doped LaGaO3 have been attributed to V++ and V3+ ions coexistent in the matrix whereas a short lived and broad band lumi nescence recorded in the 12000-15000 cm(-1) region has been attributed to t he E-2-T-2(2) transition of V2+ ions. Absorption spectra of LaGaO3 doped wi th cobalt were found to be consistent with a mixed valency system containin g Co2+ and Co3+. This activator-host combination did not show luminescence strong enough to be recorded with our detection systems. (C) 1999 Elsevier Science S.A. All rights reserved.