Vanadium in forsterite: oxidation states and structural localization in the crystals grown by the Czochralski technique

The polarized absorption spectra of vanadium-doped forsterite single crystals in the range of 300-1600 nm (6250-33000 cm(-1)) at 77 and 300 K have been investigated. All types of absorption centers were identified in the frame of crystal field theory. Crystal densities in dependence on vanadium concentration, measured by the precision floatation method, correlate with the results of structural computer modeling for different oxidation states of the dopant, It was shown that vanadium-doped forsterite crystals, grown by the Czochralski technique, contain mainly tetrahedrally coordinated V4+, ions. Partial oxidation of V4+ ions into V5+ state can be reached by oxidizing annealing of grown crystals. Octahedrally coordinated V3+ is responsible, apparently, for the absorption bands at 325, 375, 430 and 480 nm. The possibility to attribute the band at 1250 nm to V2+ ion is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.