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Author Als-Nielsen, J. ♦ Andersen, N.H. ♦ Broholm, C. ♦ Clausen, K.N. ♦ Lebech, B. ♦ Nielsen, M. ♦ Poulsen, H.F.
Sponsorship IEEE Magnetics Society
Source IEEE Xplore Digital Library
Content type Text
Publisher Institute of Electrical and Electronics Engineers, Inc. (IEEE)
File Format PDF
Copyright Year ©1965
Language English
Subject Domain (in DDC) Natural sciences & mathematics ♦ Physics ♦ Electricity & electronics ♦ Technology ♦ Engineering & allied operations ♦ Applied physics
Subject Keyword Oxidation ♦ Kinetic theory ♦ Yttrium barium copper oxide ♦ Powders ♦ Atmosphere ♦ Neutrons ♦ Diffraction ♦ Ceramics ♦ Temperature ♦ Isothermal processes
Abstract A high-resolution, multidetector neutron powder diffractometer has been constructed and used for online studies of the oxidation kinetics in ceramic powders of oxygen-deficient YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBACUO). The structural phase transition between ordered orthorhombic and disordered tetragonal phase has been studied in pure oxygen and under vacuum. A continuous transition at 655 degrees C is observed in a pure oxygen atmosphere under equilibrium conditions, whereas an irreversible transition is observed at 470 degrees C under vacuum. Reduced YBACUO corresponding to x approximately=1.0 has been obtained by evacuation at 705 degrees C and has been shown to be stable in air. The oxidation processes of reduced YBACUO in a pure oxygen atmosphere have been studied using a semidynamical stepwise increase in temperature and under isothermal conditions. The results show that the in-diffusion under oxidation of reduced YBACUO is more easily accomplished than the corresponding out-diffusion process under reduction. From the structural data it is concluded that oxidation takes place in a mixed-phase medium of coexisting tetragonal and orthorhombic phases.<<ETX>>
Description Author affiliation :: Dept. of Phys., Riso Nat. Lab., Roskilde, Denmark
ISSN 00189464
Education Level UG and PG
Learning Resource Type Article
Publisher Date 1989-03-01
Publisher Place U.S.A.
Rights Holder Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Volume Number 25
Issue Number 2
Size (in Bytes) 944.24 kB
Page Count 8
Starting Page 2254
Ending Page 2261

Source: IEEE Xplore Digital Library