Magnetic Properties of YBa₂Cu₃O_7-δMelt Textured Samples Prepared by Powder Melting Process and Quench and Melt Growth Techniques

Abstract

The microstructure and magnetic properties of the melt textured YBa2Cu3O7_δ samples prepared by the powder melting process, in which Y2Cu2O5 and BaCuO2 were used as precursors, and those prepared by the quench aud melt growth method are described and compared. The lattice parameters and Tc 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 820 A m-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 YBa2Cu3O7-δ samples are discussed.

Crystallization features of YBa2Cu3O7-δ single crystals in 2YBa4Cu3O9-δ + BaCu2O2 + CuO2 system

“…The basic methods for growing a textured compound YBa 2 Cu 3 O 7-δ are two main ones: MTG (Melt-Textured-Growth)the method is based on the growth of textured ceramics from a molten initial charge of composition YBa 2 Cu 3 O 7-δ [2][3][4][5]; QMG (Quench-Melt-Growth) method is based on the growth of textured ceramics from a molten initial charge of YBa 2 Cu 3 O 7-δ composition with an additional stage consisting in melt quenching [2-4, 6, 7]. On their basis, all other methods for obtaining a high-temperature superconductor are formed [8][9][10][11][12][13][14].…”