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Magnetic Properties of YBa_{2}Cu_{3}O_{7-δ} Melt Textured Samples Prepared by Powder Melting Process and Quench and Melt Growth Techniques

100%

Plesch G., Cígaň A., Maňka J., Bučkuliaková A., Hanic F., Buchta Š., Andrzejewski B., Stankowski J.

Acta Physica Polonica A

2000

vol. 98

issue 4

327-334

The microstructure and magnetic properties of the melt textured YBa_{2}Cu_{3}O_{7-δ} samples prepared by the powder melting process, in which Y_{2}Cu_{2}O_{5} and BaCuO_{2} were used as precursors, and those prepared by the quench and melt growth method are described and compared. The lattice parameters and T_{c} values for the samples prepared by the both techniques were similar. The penetration and the spatial distribution of the magnetic flux in the superconducting samples was imaged by means of a field-mapping device using a Hall probe. In the range of low magnetic fields up to 820Am^{-1} no significant differences in penetration of magnetic flux between the samples prepared by the powder melting process and the quench and melt growth were observed. The mapping could not resolve any grain boundaries, single grains and structural defects. By the ac and virgin volume magnetisation characteristics, which were measured in the zero-field cooled condition by a 2nd order SQUID gradiometer, no weak links were identified. Better magnetic properties of the quench and melt growth samples in high magnetic fields can be explained by the differences in microstructure and/or by the risen content of the finely dispersed 211 and Pt containing phases. The increase factor in magnetisation is about 2.5. Some aspects of the Bean model for textured YBa_{2}Cu_{3}O_{7-δ} samples are discussed.

Magnetic Properties of YBCO-PST Composites

80%

Andrzejewski B., Kaczmarek A., Stankowski J., Hilczer B., Marfaing J., Régnier S., Caranoni C.

Acta Physica Polonica A

2000

vol. 98

issue 6

739-746

The magnetic properties of granular superconductor-insulator composites were investigated. The composites were random composition of the YBa_{2}Cu_{3}O_{7-δ} (YBCO) high-temperature superconductor and Pb(Sc_{0.5}Ta_{0.5})O_{3} (PST) ferroelectric insulator. The composites exhibited lower superconducting volume ratio than the YBCO content. For samples with YBCO content low enough no global (the whole sample) and local (separated grains) superconductivity was observed. The observed decay of the superconductivity, lowering of the critical temperature, and the increase in number of paramagnetic centres as PST content increases are explained assuming reaction among YBCO and PST phases and possible formation of an additional ones, which did not exist in the initial powders.

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2 Acta Physica Polonica A

2 2000

2 Andrzejewski B.

2 Stankowski J.

1 Buchta Š.

1 Bučkuliaková A.

1 Caranoni C.

1 Cígaň A.

1 Hanic F.

1 Hilczer B.

1 Kaczmarek A.

1 Marfaing J.

1 Maňka J.

1 Plesch G.

1 Régnier S.

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Magnetic Properties of YBa_{2}Cu_{3}O_{7-δ} Melt Textured Samples Prepared by Powder Melting Process and Quench and Melt Growth Techniques

Magnetic Properties of YBCO-PST Composites