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- Title
Effects of alkali metals on the formation of Tl-1212 type phase (Tl<sub>0.85</sub>Cr<sub>0.15</sub>)Sr<sub>2−<italic>x</italic></sub>A<sub><italic>x</italic></sub>CaCu<sub>2</sub>O<sub>7</sub> with A = Li, Na and Rb.
- Authors
Nur-Akasyah, J.; Abd-Shukor, R.
- Abstract
The effects of alkali metals A = Li, Na and Rb on (Tl0.85Cr0.15)Sr2−<italic>x</italic>A<italic>x</italic>CaCu2O7 (Tl-1212) superconductors with <italic>x</italic> = 0–0.1 were studied. The samples were prepared via the solid-state reaction method. X-ray diffraction patterns showed that the formation of Tl-1212 phase was favorable when the ionic radius of the alkali metal was closer to the radius of Tl1+. Ca0.3Sr0.7CuO2 was present as a major or minor phase in some of the samples. Scanning electron micrographs showed that the grain size increased with Li, Na and Rb substitutions. The temperature-dependent electrical resistance measurements showed metallic normal state behavior for all samples with onset transition temperature, <italic>T</italic>c onset between 96 and 105 K and zero-resistance temperature, <italic>T</italic>c zero between 92 and 99 K. AC susceptibility measurement showed superconducting transition, Tcχ′<inline-graphic></inline-graphic> between 92 and 97 K. The peak temperature <italic>T</italic>p of the imaginary part of the susceptibility χ″ was the highest for Na and Rb with <italic>x</italic> = 0.1 samples (<italic>T</italic>p = 92 K). The inter-grain critical current density, <italic>J</italic>c at <italic>T</italic>p for <italic>x</italic> = 0 sample was <italic>J</italic>c (<italic>T</italic>p = 68 K) = 14 A cm−2 and for Li substituted sample with <italic>x</italic> = 0.1, <italic>J</italic>c (<italic>T</italic>p = 76 K) = 22 A cm−2. This work showed that Rb greatly enhanced the Tl-1212 phase formation due to the proximity of the Rb1+ and Tl1+ ionic radius. Na and Rb improved the transition temperature. Li, Na and Rb improved the inter-grain critical current density and increased the grain size of the samples.
- Subjects
ALKALI metals; X-ray diffraction; SUPERCONDUCTORS; SCANNING electron microscopy; GRAIN size; TRANSITION temperature
- Publication
Journal of Materials Science: Materials in Electronics, 2018, Vol 29, Issue 5, p3690
- ISSN
0957-4522
- Publication type
Article
- DOI
10.1007/s10854-017-8300-9