Abstract
Most established top seeded melt growth (TSMG) processes of bulk, single grain Y–Ba–Cu–O (YBCO) superconductors are performed using a mixture of pre-reacted precursor powders. Here we report the successful growth of large, single grain YBCO samples by TSMG with good superconducting properties from a simple precursor composition consisting of a sintered mixture of the raw oxides. The elimination of the requirement to synthesize precursor powders in a separate process prior to melt processing has the potential to reduce significantly the cost of bulk superconductors, which is essential for their commercial exploitation. The growth morphology, microstructure, trapped magnetic field and critical current density, Jc, at different positions within the sample and maximum levitation force of the YBCO single grains fabricated by this process are reported. Measurements of the superconducting properties show that the trapped filed can reach 0.45 T and that a zero field Jc of 2.5 × 104 A cm−2 can be achieved in these samples. These values are comparable to those observed in samples fabricated using pre-reacted, high purity commercial oxide precursor powders. The experimental results are discussed and the possibility of further improving the melt process using raw oxides is outlined.
Highlights
(RE)–Ba–Cu–O [(RE)BCO] bulk high temperature superconductors (HTS), where RE is a rare-earth element or Y, have attracted considerable attention since the discovery of the YBCO system in 1987 [1]
Yang et al [19, 20] further developed the modified top seeded infiltration growth (TSIG) process in which BaCuO2 is the only required prereacted precursor powder. These studies indicate that pure phase Y-211 and Y-123 precursor powders are not essential to achieve a complete peritectic reaction and the subsequent growth of YBCO single grains in a seeded melt process, and that it is possible to use a mixture of raw oxides, from which Y-123 and Y-211 form via chemical reaction during melt processing, rather than pure Y-123 and Y-211 to fabricate large YBCO single grains
It is reasonable to assume that a mixture of raw oxides, most of which would react into Y-123 and Y-211 in both top seeded melt growth (TSMG) and TSIG, can be used as precursor powders in both processing techniques
Summary
(RE)–Ba–Cu–O [(RE)BCO] bulk high temperature superconductors (HTS), where RE is a rare-earth element or Y, have attracted considerable attention since the discovery of the YBCO system in 1987 [1]. The synthesis of pure phase precursor powder by solid-state reaction can take up to a week, which prolongs the fabrication process and leads to a low efficiency and high cost process This additional processing limits further the batch production of YBCO bulk superconductors and its potential for commercially viable applications. Yang et al [19, 20] further developed the modified TSIG process in which BaCuO2 is the only required prereacted precursor powder These studies indicate that pure phase Y-211 and Y-123 precursor powders are not essential to achieve a complete peritectic reaction and the subsequent growth of YBCO single grains in a seeded melt process, and that it is possible to use a mixture of raw oxides, from which Y-123 and Y-211 form via chemical reaction during melt processing, rather than pure Y-123 and Y-211 to fabricate large YBCO single grains. A standard YBCO single grain fabricated using commercial Y-123 and Y-211 precursor powders
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