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Optical Absorption Study of the Reduction Kinetics of Rutile Crystals
Author(s) -
CARNAHAN R. D.,
BRITTAIN J. O.
Publication year - 1965
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1965.tb14762.x
Subject(s) - rutile , kinetics , analytical chemistry (journal) , activation energy , arrhenius equation , absorption (acoustics) , diffusion , materials science , electrical resistivity and conductivity , absorption spectroscopy , atmospheric temperature range , reaction rate constant , attenuation coefficient , crystal (programming language) , chemistry , mineralogy , optics , thermodynamics , composite material , physics , organic chemistry , chromatography , quantum mechanics , electrical engineering , engineering , computer science , programming language
The early stages of the reduction kinetics of single‐crystal rutile, TiO 2 , were studied by optical absorption techniques for specimens re duced in the range 550° to 760°C at a constant vacuum level of 10 −3 mm Hg. When reduced to a room‐temperature resistivity value of ∼10 3 ohm‐cm, rutile shows a blue coloration as a re sult of a broad infrared absorption band centered at a wavelength of 1.2μ. The kinetics of growth of the optical absorption coefficient at 1.2μ fit a parabolic relation of the form (Δα) 2 = K′t. The Arrhenius rate constant, K′ , exhibited an activation energy of 111 ± 9 kcal/mole which is ∼50% too high for the diffusion of oxygen in rutile. It is postulated that the defect center is likely to be a Ti interstitial and that the kinetics reflect the self‐diffusion of Ti as the rate‐con trolling mechanism.