Ca-substitution and O-doping effects in superconducting Cu(Ba0.8Sr0.2)2(Yb1-xCax)Cu2O6+z obtained from neutron diffraction refinements

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Volume Title
School of Chemical Technology | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
1999
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Mcode
Degree programme
Language
en
Pages
4378-4385
Series
Physical Review B, Volume 60, Issue 6
Abstract
Distinct calcium and oxygen doping effects were studied in the Cu(Ba0.8Sr0.2)2(Yb1−xCax)Cu2O6+z (Cu−1212:P) system by means of neutron diffraction and superconducting quantum interference device experiments in the wide substitution ranges of 0<~x<~0.35 and 0<z<1. The effectiveness of the two different ways to introduce holes into the CuO2 planes was compared both in respect to the capability to increase Tc and in terms of the hole production as estimated from neutron-diffraction data via bond-valence-sum calculation. Oxygen doping was found to increase the hole concentration less efficiently, and further, at a certain hole concentration value higher Tc values were obtained with calcium substitution than with oxygen doping. The two different hole-doping methods exhibited also different Tc vs Cu-O bond length relations. As a conclusion, the possible roles of the hole distribution in the in-plane Cu-O bond and the flatness of the CuO2 planes in determining the superconducting properties were recognized.
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Keywords
superconductors, neutron diffraction, oxygen doping, calcium
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Citation
Karppinen, Maarit & Yamauchi, H. & Fujinami, K. & Nakane, T. & Peitola, K. & Rundlöf, H. & Tellgren, R. 1999. Ca-substitution and O-doping effects in superconducting Cu(Ba0.8Sr0.2)2(Yb1-xCax)Cu2O6+z obtained from neutron diffraction refinements. Physical Review B. Volume 60, Issue 6. 4378-4385. ISSN 1550-235X (electronic). DOI: 10.1103/physrevb.60.4378.