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Title: Infrared optical properties of α-alumina with the approach to melting: γ-like tetrahedral structure and small polaron conduction

The normal spectral emittance of α-Al{sub 2}O{sub 3} single crystal has been measured from room temperature up to the liquid state and from 20 cm{sup −1} up to 10 000 cm{sup −1}, in two polarization configurations. The spectra were fitted with a semi-quantum dielectric function model. AlO{sub 4} structure units are revealed within the phonon spectral range more than a hundred degrees below the melting point when heating from the solid state. In parallel, the anomalous increase of emittance observed within the transparency spectral range with the approach to melting appears strongly correlated. Implications on the electronic structure are discussed: the existence of small polaron conduction is suggested which has never been mentioned before.
Authors:
 [1] ;  [2] ; ;  [1] ;  [2] ;  [1]
  1. CNRS, UPR 3079 CEMHTI, Orléans 45071 (France)
  2. (France)
Publication Date:
OSTI Identifier:
22266171
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 22; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; ALUMINIUM OXIDES; CONFIGURATION; DIELECTRIC MATERIALS; ELECTRONIC STRUCTURE; HEATING; LIQUIDS; MELTING; MELTING POINTS; MONOCRYSTALS; OPACITY; PHONONS; POLARIZATION