The influence of charge transfers effects in monazite-type LaVO4 and perovskite-type LaVO3 prepared by sol-gel acrylamide polymerization

摘要

Core-hole spectroscopy such as X-ray absorption spectroscopy (XAS) is useful to determine the electronic structure of strongly correlated and strongly hybridized compounds such as vanadates. Monazite-type LaVO4 and perovskite-type LaVO3 are good candidates to elucidate the electronic structure through the vanadium L-2,L-3 edge. LaVO4 was prepared by sol-gel acrylamide polymerization and solid-state reaction. LaVO3 was obtained by reduction of LaVO4 using Zr as gatherer. Monoclinic crystal phase for LaVO4 and orthorhombic crystal phase for LaVO3 were confirmed by the Rietveld refinement of X-ray diffraction patterns. XAS comparison between Vanadium L-2,L-3 edge confirms the presence of V5+ for the monazite and V3+ for the orthorhombic perovskite. Multiplet calculations including crystal field and charge transfer effects (CTM) were performed in order to elucidate the tetraginal (D-4h symmetry) parameters Dq, Ds and Dt, the charge transfer energy Delta, and d-d Coulomb repulsion energy U parameters. CTM confirms for LaVO3 the strong V 3d-O 2p hybridization with a significant contribution of covalent charatter due to the delocalization of 3d electrons. For LaVO4 this work suggest the reclassification of this band insulator as charge transfer insulator that shows a significant contribution of ionic character. (C) 2016 Elsevier B.V. All rights reserved.