研究目的
To investigate the effect of size and aspect ratio on the trapped field properties of single grain Y-Ba-Cu-O bulk superconductors, and to explore the potential of using assemblies of smaller samples for engineering applications.
研究成果
The size and aspect ratio significantly affect trapped field properties, with optimum H/R between 0.67 and 1 for saturation. Smaller samples have higher average Jc, and stacking multiple samples can enhance trapped fields and achieve more uniform distributions. This supports the use of assemblies in applications like MRI, but further research is needed for optimization and generalization.
研究不足
The study is limited to YBCO superconductors at 77 K; results may not generalize to other (RE)BCO systems or temperatures. The model comparisons assume uniform Jc, which is not accurate due to microstructural non-uniformities. Sample sizes are relatively small (up to 25 mm diameter), and the slicing process may introduce defects. The total flux is calculated in arbitrary units, not absolute values.
1：Experimental Design and Method Selection:
The study used an experimental approach to fabricate YBCO single grains via top-seeded melt-growth (TSMG) process, measure trapped fields and total flux at 77 K using field-cooling magnetization, and compare results with theoretical models like Eisterer's and Chen's formulas.
2：Sample Selection and Data Sources:
Three cylindrical YBCO single grains of diameters 16 mm, 20 mm, and 25 mm were fabricated from precursor powders. Samples were sliced successively to vary height and aspect ratio, with trapped field measurements taken at different heights above surfaces.
3：List of Experimental Equipment and Materials:
Equipment includes a box furnace for TSMG, isostatic press at 2000 bar, Turbula mixer, Hall probe array for field measurements, and diamond blade for slicing. Materials include YBa2Cu3O7?δ and Y2BaCuO5 powders, CeO2, Yb2O3, NdBa2Cu3O7?δ seeds, and liquid nitrogen for cooling.
4：Experimental Procedures and Operational Workflow:
Precursor powders were mixed and pressed into pellets, seeded, and processed in a furnace with specific heating profiles. Samples were oxygenated, magnetized by field-cooling in
5：4 T field, and trapped fields measured at 5, 0, and 5 mm above surfaces using a rotating Hall probe array. Samples were sliced incrementally, and measurements repeated. Data Analysis Methods:
Trapped field distributions were analyzed using OriginTM software to calculate total flux by summing positive Bz values. Critical current density Jc was estimated using Chen's formula, and results were compared qualitatively with Eisterer's model.
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