Superconductivity and processing of single Bi?O layered cuprates in the (Bi, Pb)?Sr?(Ca, Y)?Cu?O system

Zoller, P.; Gläser, Jochen; Ehmann, A.; Schulz, Christoph; Wischert, W.; Kemmler‐Sack, S.; Nissel, T.; Huebener, R. P.

doi:10.1007/bf01313848

Cited by 16 publications

(3 citation statements)

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“…From these facts, we believe that the 2212 phase is responsible for superconductivity and not the 1212 phase. Nevertheless, there is a discrepancy between the maximum critical temperatures known for the 2212 phase (T c,max ‫ס‬ 95 K) and those reported for the 1212 phase (T c,max ‫ס‬ 102 K, from Zoller et al 15 ). However, in our opinion, only a phase-pure 1212 sample or a single crystal could establish whether or not this phase is superconducting.…”

Section: Discussionmentioning

confidence: 79%

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Phase Equilibria and Superconducting Properties of BiSr₂YCu₂O₇ (1212 Phase)

Kaesche¹,

Majewski²,

Aldinger

1999

Journal of the American Ceramic Society

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Phase equilibria of the quasi‐quaternary system BiO1.5–SrO‐YO1.5–CuO have been studied at a temperature of 950°C in air, with special regard to the 1212 phase. The 1212 phase reveals only very small changes in the cation ratio. Single‐phase samples exist for (Bi0.24–0.36Cu0.42‐0.55)–Sr2Y1.27Cu2Oy compositions. The bismuth‐rich composition of the 1212 phase is in thermodynamic equilibrium with a liquid and the 2212 phase, whereas the copper‐rich composition is in equilibrium with five other phases. The influence of combined calcium and lead doping also has been studied. Exceeding the calcium saturation of the 1212 phase increases the amount of 2212 as a secondary phase. Single‐phase 1212 samples do not show any superconductivity in either the as‐prepared or the post‐annealed state. The only compositions with bulk superconductivity are those with calcium and lead doping after annealing at a temperature of 980°C. The superconductivity is attributed to the 2212 phase crystallizing from the melt during slow cooling.

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Section: Discussionmentioning

confidence: 79%

“…Combined calcium and lead doping has been studied in detail, because of various reports 6,7,15 in regard to the positive influence of these elements on the superconducting properties. The cation ratio of Bi 0.4 Pb 0.4 Sr 2 Y 1−x Ca x Cu 2.2 O y was taken from literature.…”

Section: (3) Calcium and Lead Dopingmentioning

confidence: 99%

Phase Equilibria and Superconducting Properties of BiSr₂YCu₂O₇ (1212 Phase)

Kaesche¹,

Majewski²,

Aldinger

1999

Journal of the American Ceramic Society

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“…It starts with the selection of starting materials. Oxides and carbonates are preferentially used whereas nitrates are claimed to increase the amount of impurity phases [22,23]. Likewise the substitution of PbO 2 for PbO increases the purity of the samples [23].…”

Section: Introductionmentioning

confidence: 99%

Powder synthesis of (Bi, Pb)-1212 superconductors

Schneider¹,

Köbel²,

Gauckler³

2000

Supercond. Sci. Technol.

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The influence of the stoichiometry of the (Bi,Pb)Sr2(Ca,Y)Cu2Oz on its critical temperature and phase purity was investigated. High yttrium and lead contents raise the 1212 phase content to 95%, whereas the highest critical temperature of 97 K was measured inductively for Bi0.4Pb0.35Sr2Ca0.3Y0.7Cu2.05Oz. The transition from the normally conducting to the superconducting state takes place over a broad temperature regime of at least 40 K. Different 1212 grains within one sample have different cation stoichiometries leading to variable superconducting properties. Furthermore, we show that the ordinary lattice sites of bismuth inside an individual grain are occupied by several different cations, such as Bi, Pb, Cu and Sr and that that of calcium may be occupied by Ca, Y, Sr and Cu. Under optimised processing conditions the stoichiometry Bi0.2Pb0.6Sr1.9Ca0.3Y0.7Cu2.3Oz leads to > 95% phase pure Bi-1212 material. The material is sintered at a temperature 20 °C below the melting temperature of the 1212 compound in air. At this temperature the phase forms within 10 min from the starting oxide and carbonate powders. For longer sintering times the phase decomposes due to Bi and Pb evaporation. When furnace cooled, the 1212 phase remains stable.

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