Effect of Ultra-sonicated Y2BaCuO5 on Top-Seeded Melt Growth YBa2Cu3Oy Bulk Superconductor
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In this work, we tried to improve the superconducting performance of bulk YBa2Cu3Oy (Y123) superconductors via Y2Ba1Cu1O5 (Y211) secondary phase refinement. A novel method of ultra-sonication was used to refine the Y211 secondary phase particles. The Y211 powder was treated by ultra-sonication for 0 to 80 min with steps of 20 min, keeping the power (300 W) and frequency (20 kHz) constant. For synthesis of the YBCO bulk, we employed top-seeded melt growth (TSMG) with Pt addition. Magnetization measurements showed a superconducting transition temperature at around 91 K, irrespective of ultra-sonication parameters. Interestingly, critical current density and trapped field were found to be proportional to the ultra-sonication duration. YBCO bulk sample (20 mm diameter, 7 mm in thickness) fabricated for 80 min ultra-sonicated Y211 showed a maximum trapped field of 0.42 T at 77 K, 0.3 mm above the top surface. The improved trapped field values are explained on the basis of improvements in the microstructure.
KeywordsYBa2Cu3Oy Y2BaCuO5 Top-seeded melt growth Ultra-sonication Critical current density
Superconducting properties of Y123 bulk superconductors (with refined Y211 via ultra-sonication)
Jc (self-field) (kA/cm2)
Trap field (T)
In our previous work, we tried to synthesize samples by infiltration growth using ultra-sonicated Y211 . There we synthesized bulk with improved properties because of Y211 size reduction. In this paper, we studied the optimization of ultra-sonication process parameters for producing fine Y211 particles and effect of refined Y211 particles size on the superconducting properties of melt grown YBCO bulk superconductors. YBCO single grain superconductors of 20 mm were fabricated by top-seeded melt growth. Systematic study was done by varying the ultra-sonication time, and superconducting properties were compared with highlight the best processing conditions.
3 Results and Discussion
Among various durations, 80 min of ultra-sonication seemed to be the optimum for refining Y211 powder based on the particle size and uniform shape of Y211 powder. We have successfully prepared YBCO bulk consisting of Y123 and Y211 mixed in a molar ratio of 10:5 with 0.5 wt% Pt by TSMG processing. XRD clearly shows that all the bulk Y123 samples have good texture and pure single grain nature. All samples exhibited superconductivity with Tc ~ 92.8 K and sharp superconducting transitions. The highest critical current density (Jc) was observed in 80-min ultra-sonicated bulk which was measured to be 47 kA/cm2 at self-field and 77 K. For the same bulk at 77 K, the trapped field measurements exhibited single uniform conical peak with the maximum value of 0.42 T at the center. SEM observations showed that the particle sizes of the most Y211 particles have been reduced to 1–2 μm and uniformly dispersed within the final Y123 matrix which led to the improvement in the superconducting properties of Y123 bulk superconductor. The ultra-sonication technique has great potential to refine Y211 particles for mass production of large high performance YBCO bulk superconductors for practical applications. In addition, this technique is cost-effective and brings nearly no contamination. All these features make it a best choice for mass production.
This work was partly supported by Shibaura Institute of Technology (SIT) Research Center for Green Innovation and Grant-in-Aid FD research budget code 112282. Two of the authors (Sai Srikanth Arvapalli and Sunsanee Pinmangkorn) acknowledge the support from SIT for providing the financial support for the doctoral program.
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