Effect of site-selective substitution in bulk superconducting Tl{sub 2}Ba{sub x}CaCu{sub 2}O{sub 8}
- Univ. of Colorado, Boulder, CO (United States)
Magnetization measurements were carried out on bulk Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} (referred to as Tl-2212) and on various site-selective substituted Tl-2212 samples. At 5K between O and 4.5 T, the 5 at. % Mg-doped Tl-2212 (Tl,Mg-2212) samples displayed enhanced pinning as demonstrated by a field-dependent increase of the magnetic critical-current density J{sub c} by 18 to 25 percent over that of pristine Tl-2212. Excess Mg (10-15 at. %), however, is deleterious. Rietveld refinement of the x-ray diffraction pattern showed Mg on the Tl sites. Auger electron spectroscopy analysis showed part of the Mg on grain boundaries. The flux-creep activation energies are higher for flux expulsion than for flux penetration in both Tl-2212 and Tl, Mg-2212 samples; the latter displays higher individual values. Their results demonstrate an increase in the number density of flux lines as a result of increased density of atomic-size-structural defects by Mg (5 at. %) doping. In the Tl{sub 2{minus}y}Ba{sub 2}(Ca{sub 1{minus}z}Y{sub 2})Cu{sub 2}O{sub 8{minus}x}(z = 0-0.3; single phase; x and y represent oxygen and thallium vacancies) system also studied, the T{sub c} decreases as z increases. At x = 0.3, the sample becomes an antiferromagnetic semiconductor.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 433420
- Journal Information:
- Journal of Electronic Materials, Journal Name: Journal of Electronic Materials Journal Issue: 10 Vol. 22; ISSN JECMA5; ISSN 0361-5235
- Country of Publication:
- United States
- Language:
- English
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