P K Pujari
Articles written in Bulletin of Materials Science
Volume 14 Issue 3 June 1991 pp 681-686 International Conference On Superconductivity—II
Doppler-broadened annihilation radiation spectra have been measured as a function of temperature from 77 K to 300 K, for several high temperature oxide superconductors viz single-phase YBCO, single- and mixed-phase Tl-Ca-Ba-Cu-O and Bi-Ca-Sr-Cu-O compounds. The temperature-dependent parameters extracted respond to a change at the onset of superconducting transition. The observations point to involvement of oxygen valence electrons at the onset of superconducting transition. Also a possible structural change and/or increase in electron density at the oxygen vacancy/defect sites seem to accompany the transition. In addition, the parameters derived are seen to be sensitive to the presence of more than one superconducting phases in mixed phase samples.
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