Infiltration-growth processing of superconductor
TL;DR: In this paper, the melting process of Sm-123 is done by infiltrating liquid phases into an Sm-211 preform and allowing the growth of SM-123 to take place.
Abstract: Melt processing of (Sm-123) is done by infiltrating liquid phases into an Sm-211 preform and allowing the growth of Sm-123 to take place. The melt-textured samples are found to be free of macrodefects, and the microstructure contains uniformly distributed fine-sized Sm-211 particles. The behaviour of the critical current density of the samples in high fields is reported here.
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TL;DR: In this article, a single domain Y?Ba?Cu?O (YBCO) composed of a Y-123 superconducting bulk matrix with discrete, non-superconducting Y2BaCuO5 (Y-211) phase inclusions has been fabricated by a seeded infiltration and growth (IG) technique in the form of cylindrical pellets up to 32mm in diameter.
Abstract: Single domain Y?Ba?Cu?O (YBCO) composed of a YBa2Cu3Oy (Y-123) superconducting bulk matrix with discrete, non-superconducting Y2BaCuO5 (Y-211) phase inclusions has been fabricated by a seeded infiltration and growth (IG) technique in the form of cylindrical pellets up to 32?mm in diameter. Sample shrinkage in the radial direction for single domains prepared by this technique is relatively low at 5% and independent of sample size, in contrast to the shrinkage observed in samples grown by conventional melt processing, which increases significantly with increasing sample diameter. Furthermore, samples grown by the IG technique exhibit low porosity of typically 0.9% of the bulk volume fraction, compared with a corresponding value of around 4.9% observed in samples fabricated by conventional melt processing. Fine Y-211 particles were observed to be embedded within the Y-123 superconducting matrix for the IG processed samples, leading to a high critical current density, Jc, of over 100?000?A?cm?2 at 77.3?K in self-field. The distribution of Y-211 particles in the IG sample microstructure, however, was inhomogeneous (unlike in previous reports), which leads to a variation in the spatial distribution of Jc. The volume fraction of Y-211 in the vicinity of the seed crystal (i.e.?corresponding to the initial c-sector growth stage), in particular, is typically around 5%, compared with a value of up to 30% in the a growth sectors more distant from the seed crystal (which corresponds well to the theoretical value for the sample composition studied here). The volume fraction of Y-211 inclusions in the c growth sector more distant from the seed was around 22%. Finally, a trend of the variation in the distribution of Y-211 particles in the Y-123 matrix grown by the IG technique was similar to that in sample grown by conventional melt processing.
98 citations
TL;DR: In this paper, an infiltration and top seed growth method (ITSG) was used to grow a single grain of YBa2Cu3O7−x (Y123) bulk material, which is controlled by seeding the Y2BaCuO5 (Y211) preform with a Sm123 or MgO seed crystal.
Abstract: An infiltration and top seed growth method (ITSG), has been successfully used to grow a single grain of YBa2Cu3O7−x (Y123) bulk material. The nucleation of Y123 grain is controlled by seeding the Y2BaCuO5 (Y211) preform with a Sm123 or MgO seed crystal. Various configurations influencing the liquid infiltration such as that due to capillarity or gravitational force have been studied. The resulting mono-domain Y123 samples are found to be free of macrocracks, a negligible shrinkage and a microstructure with uniformly distributed fine Y211 particles. The superconducting properties of the final Y123/Y211 samples are discussed.
62 citations
TL;DR: In this paper, a large, single grains of Y?Ba?Cu?O (YBCO) bulk superconductor composed of a YBa2Cu3O7?? matrix with Y2BaCuO5 (Y-211) inclusions have been fabricated using a seeded infiltration and growth (IG) process.
Abstract: Large, single grains of Y?Ba?Cu?O (YBCO) bulk superconductor composed of a YBa2Cu3O7?? (Y-123) matrix with Y2BaCuO5 (Y-211) inclusions have been fabricated using a seeded infiltration and growth (IG) process. Y-211 precursor pellets prepared from powders containing different Y-211 particle sizes were processed by the seeded IG technique to investigate the effect of Y-211 size on the single grain microstructure. The superconducting properties of the single grains fabricated in this study are observed to correlate well with the variation in Y-211 particle size in the fully textured Y-123 phase matrix. The critical current density, Jc, in particular, has been observed to increase from 68?000?A?cm?2 for a reference sample to 94?000?A?cm?2 at 77?K in self-field for a sample prepared using refined Y-211 precursor powder with added platinum oxide.
52 citations
TL;DR: In this paper, the authors reported record high current densities of 230 kA cm − 2 at zero field, and in excess of 10kA cm−2 up to 7 T at 77 K, in YBa2Cu3O7 − δ (Y-123) superconductors fabricated by a modified infiltration growth (IG) process.
Abstract: We report record high current densities of 230 kA cm − 2 at zero field, and in excess of 10 kA cm − 2 up to 7 T at 77 K, in YBa2Cu3O7 − δ (Y-123) superconductors fabricated by a modified infiltration growth (IG) process. This was accomplished by optimizing the Y2BaCuO5 (Y-211) preform, into which liquid phases were infiltrated, through a combination of high pressure compaction and limiting the sintering temperature. The optimized sample yielded a Y-123 superconductor with a uniform distribution of fine-grained Y-211. Strong and almost invariant flux pinning observed to high fields up to 7 T, suggest a temperature independent flux pinning mechanism originating from defects in the size range 15–50 nm. Since the present sample has no added grain refiners, nano-sized dopants or mixed rare earths leading to low Tc solid solutions, a unique opportunity presents itself to investigate the cause of the enhanced flux pinning to high fields. We have therefore investigated our samples by transmission electron microscopy, and the studies revealed the presence of domains in the sample with nano-sized defects starting from the domain boundaries, as a possible source of enhanced flux pinning.
41 citations
TL;DR: In this article, the effects of Gd 2 BaCuO 5 (Gd211) addition on the microstructure and J c -B properties of oxygen-controlled-melt-growth (OCMG)-processed (Nd, Eu, Gd)-Ba-Cu-O system with scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and magnetization measurements were investigated.
Abstract: We have investigated the effects of Gd 2 BaCuO 5 (Gd211) addition on the microstructure and J c – B properties of oxygen-controlled-melt-growth (OCMG)-processed (Nd, Eu, Gd)–Ba–Cu–O system with scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and magnetization measurements. Compositional analyses revealed that small RE 2 BaCuO 5 (RE211; RE: rare earth elements) particles consist mainly of Gd in the RE site, while large RE211 particles contain Nd, Eu and Gd despite the fact that only Gd211 was added to the system. Both zero field and peak J c increased with increasing Gd211 content; however, J c values were decreased when the amount of Gd211 reached 40 mol%. The sample (Nd, Eu, Gd)Ba 2 Cu 3 O y added with 30 mol% of second phase Gd211 showed respective critical current densities of 71 000 and 52 000 A/cm 2 in 0 T and 2.6 T at 77 K for fields parallel to the c -axis. These results indicate that Gd211 addition to (Nd, Eu, Gd)–Ba–Cu–O is effective in improving J c values through fine dispersion of Gd211.
36 citations
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TL;DR: A liquid phase processing method for the fabrication of bulk YBa2Cu3Ox superconductors with large current carrying capacity has been developed in this paper, where a cooling rate of 1'°C/h in this temperature range has yielded a microstructure with long plate type, thick grains oriented over a wide area.
Abstract: A liquid phase processing method for the fabrication of bulk YBa2Cu3Ox superconductors with large current carrying capacity has been developed. Slow cooling through the peritectic transformation (1030–980 °C) has been shown to control the microstructure of these superconductors. A cooling rate of 1 °C/h in this temperature range has yielded a microstructure with long plate type, thick grains oriented over a wide area. Current density up to 18 500 A/cm2 has been obtained by continuous direct current measurements and in excess of 62 000 A/cm2 with pulse current of 10 ms duration and 75 000 A/cm2 using 1 ms pulse. The strong magnetic field dependence observed in sintered bulk 1‐2‐3 superconductors is also minimized to a large extent where a current density in excess of 37 000 A/cm2 is obtained in a field of 6000 G.
705 citations
TL;DR: The present work demonstrates that problems caused by low critical current densities and significant deterioration in weak magnetic fields can be overcome through proper microstructural control using molten oxide processing.
Abstract: The progress toward major applications of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$-type high-${T}_{c}$ superconductors has been hindered by low critical current densities (${J}_{c}$) and their significant deterioration in weak magnetic fields. The present work demonstrates that these problems can successfully be overcome through proper microstructural control using molten oxide processing. Melt-textured growth of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ from a supercooled melt created an essentially 100% dense structure consisting of locally aligned, long, needle-shaped grains (typically 40--600 \ensuremath{\mu}m in length). The needles appear to have their long axes parallel to the conduction plane (basal plane) of the orthorhombic structure, with a low-angle orientation change between adjacent grains. This new microstructure, which completely replaces the previous granular and random structure of the sintered precursor, exhibits a dramatically higher transport ${J}_{c}$ (7400 A/${\mathrm{cm}}^{2}$ at 77 K) than the typical sintered materials (${J}_{c}$=150--600 A/${\mathrm{cm}}^{2}$). Even more significant is the much reduced field dependence of ${J}_{c}$(\ensuremath{\approxeq}1000 A/${\mathrm{cm}}^{2}$ at H=1 T as compared to \ensuremath{\approxeq}1 A/${\mathrm{cm}}^{2}$ in the sintered structure), indicating that the coupling between grains is much stronger in the new structure. The mechanism responsible for the suppressed weak-link behavior in the melt-textured material is inferred to be the combined effects of the densification, alignment of crystals, and formation of cleaner grain boundaries.
494 citations
TL;DR: In this paper, the authors showed that rare earth (RE) ions with large radii exhibit relatively low T c due to the presence of RE-Ba solid solution and that this solid solution can be suppressed if these superconductors are melt processed in a reduced oxygen atmosphere.
Abstract: REBa2Cu3Oy superconductors with rare earth (RE) ions with large radii (RE: La, Nd, Sm) exhibit relatively low T c due to the presence of RE-Ba solid solution. We have found that this solid solution can be suppressed if these superconductors are melt processed in a reduced oxygen atmosphere. We have also found that critical current densities of these superconductors are higher than those of melt processed YBa2Cu3Oy with fine Y2BaCuO5 inclusions in a high field region. The irreversibility line was also shifted toward the higher H-T region. We believe that flux pinning in these superconductors is ascribable to a finely distributed RE(Ba1-x , REx )2Cu3Oy phase in a good superconductive matrix.
301 citations
TL;DR: In this paper, the effects of various oxygen partial pressures (P O2) during melt processing on the superconducting properties of fabricated NdBa2Cu3Oy (Nd123) superconductors have been systematically investigated.
Abstract: The effects of various oxygen partial pressures (P O2) during melt processing on the superconducting properties of fabricated NdBa2Cu3Oy (Nd123) superconductors have been systematically investigated. Unlike in air or O2, samples melt-processed in reduced oxygen atmospheres exhibited unprecedentedly high T c's of 95–96 K with a sharp superconducting transition. Especially, for a sample melt-processed in 0.1% O2 in Ar, the magnetization hysteresis ( M-H ) loop was kept open up to 7 T at 77 K and for the field parallel to the c-axis of the sample (H//c), implying that very effective flux pinning can be achieved in high magnetic fields.
133 citations
01 Oct 1991-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: The Lanxide Corporation as mentioned in this paper developed and commercialized novel technologies for ceramic matrix and metal matrix composites, based on the use of a unique directed-metal-oxidation process to grow ceramic matrices around pre-placed composite fillers or reinforcements.
Abstract: Lanxide Corporation is developing and commercializing novel technologies for ceramic matrix and metal matrix composites. The ceramic composite technology is based on the use of a unique directed-metal-oxidation process to grow ceramic matrices around pre-placed composite fillers or reinforcements. The metal matrix composites are made by a pressureless molten metal infiltration process involving excellent wetting of the reinforcement by the matrix alloy. This paper provides an overview of the processing methods, a description of some of the composites that have been made and their key properties, and an indication of some of the applications being addressed with these materials.
88 citations