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Title: Anomalous structural disorder and distortion in metal-to-insulator-transition Ti{sub 2}O{sub 3}

Mott proposed that impurity bands in corundum-symmetry Ti{sub 2}O{sub 3} at high temperatures caused a collapse in the bandgap. However, the origin of the impurity bands has not yet been clarified. We examine the local structural properties of metal-to-insulator-transition Ti{sub 2}O{sub 3} using in-situ x-ray absorption fine structure (XAFS) measurements at the Ti K edge in the temperature range from 288 to 739 K. The Ti{sub 2}O{sub 3} powder is synthesized by using a chemical reaction method. X-ray diffraction (XRD) measurements from Ti{sub 2}O{sub 3} with a Rietveld refinement demonstrate a single-phased R-3c symmetry without additional distortion. Extended-XAFS combined with XRD reveals a zigzag patterned Ti position and an anomalous structural disorder in Ti-Ti pairs, accompanied by a bond length expansion of the Ti-Ti pairs along the c-axis for T > 450 K. The local structural distortion and disorder of the Ti atoms would induce impurity levels in the band gap between the Ti 3d a{sub 1g} and e{sub g}{sup π} bands, resulting in a collapse of the band gap for T > 450 K.
Authors:
; ; ;  [1] ;  [2]
  1. Department of Physics Education and Institute of Fusion Science, Jeonbuk(Chonbuk) National University, Jeonju 561-756 (Korea, Republic of)
  2. Department of Physics, Yanbian University, Yanji 133002 (China)
Publication Date:
OSTI Identifier:
22494866
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 119; Journal Issue: 1; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; ABSORPTION SPECTROSCOPY; BOND LENGTHS; CHEMICAL REACTIONS; CORUNDUM; ELECTRONIC STRUCTURE; FINE STRUCTURE; IMPURITIES; METALS; SYMMETRY; TEMPERATURE RANGE 0400-1000 K; TITANIUM OXIDES; X RADIATION; X-RAY DIFFRACTION; X-RAY SPECTROSCOPY