On the solid solutions in the systems Bi2Sr2Ca1−xYxCu2O8+δ, Bi2Sr2−xLaxYCu2O8+δ and Bi2Sr2Y1−xCexCu2O8+δ
1989; Elsevier BV; Volume: 157; Issue: 3 Linguagem: Inglês
10.1016/0921-4534(89)90282-7
ISSN1873-2143
AutoresS. Olivier, Pim Groen, C. J. van der Beek, H.W. Zandbergen,
Tópico(s)Methane Hydrates and Related Phenomena
ResumoSolid solutions of Bi2Sr2Ca1−xYxCu2O8+δ, Bi2Sr2−xLaxYCu2O8+δ and Bi2Sr2Y1−xCexCu2O8+δ have been investigated. In the system Bi2Sr2Ca1−xYxCu2O8+δ the most significant feature is a drop in the length of the c axis from 3.08 nm for the x < 0.25 to 3.02 nm for x > 0.35. With increasing amount of Ce the length of the c axis increases up to 3.08 nm. This is due to the substitution of Sr on the Ca site. In the system Bi2Sr2−xLaxYCu2O8+δ increase of La leads to Sr partially occupying the Ca site. The Y rich material shows a significant difference between the a and the b axis. Incorporation of 20% of Y does not lead to a significant drop in Tc. When the surplus of charge due to the substitution by cations with a higher valency is more than +0.30 the material is not superconducting anymore. Often a composition range in x is obtained, with a width of at least 0.2. The observed change in the c axis and the superconducting properties is explained with a model with extra oxygen in the BiO layers. With mainly Sr on the Sr site the extra amount of oxygen seems to be restricted to 0.25 per BiO unit.
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