Effective pore control and critical current density in liquid infiltration growth processed Y-123 superconductors with Ag addition

Abstract

The effect of a sintered density (open porosity) of Y 2 BaCuO 5 (Y211) pre-forms on the final porosity and Y211 size within YBa 2 Cu 3 O 7−y (Y-123) products was systematically studied in liquid infiltration growth (LIG) processed Y-123 bulk superconductors with Ag addition. To prepare Y211 pre-forms of various densities, Y211 powder compacts were sintered in air at various temperatures of 900-1200 • C. The single-grain Y-123 bulk superconductors were fabricated by the LIG process with top seeding. It was found that the porosity of the final Y-123 product was fairly dependent on the Y211 pre-form density. When a Y211 pellet of a high density was used as a pre-form for the LIG process, the porosity of the final Y-123 product was greatly reduced. In addition to the reduced porosity, the enhanced Y211 refinement was achieved for the Y-123 product prepared using the dense Y211 pre-form, resulting in the improved critical current density (J c ). The Ag addition was also helpful in eliminating the spherical pores through pore filling with a silver melt. The pore elimination and Y211 refinement mechanism in the LIG-processed Y-123 bulks were explained in terms of the liquid capillary movement and Ag melt and particle coarsening at the (Y211 + melt) state.

Record critical current densities in IG processed bulk YBa2Cu3Oy fabricated using ball‐milled Y2Ba1Cu1O5 phase

“…4). The obtained J c values are very high as compared to previous reports [20,21,26]. Up to date such high critical currents have not been observed on melt-grown Y-123 material but already reported in Y-123 system by introducing nanoscale defects through neutron irradiation [27].…”

“…Further, the sample producing normal Y‐211 powders showed a very sharp and record‐high superconducting transition with a T c of 93.2 K and a transition width Δ T c of 0.7 K (see inset of Fig. ), which is somewhat higher as recently reported for Y‐123 material produced in IG process . However, the ball‐milled Y‐211 added sample shows a slightly lower superconducting transition temperature than the IG‐processed Y‐123 material produced from normal Y‐211 material, which indicates that a Zr ball contamination for the long time ball milling process occurs, which was also observed in earlier reports on LRE‐123 material produced by the OCMG process .…”

“…Recently, Pravan Kumar Naik et al reported the effect of the choice of IG‐temperature for Y‐123 material, i.e., 1040 and 1100 °C and studied the field dependence of the critical current density at different temperatures ranging from 15 to 77 K. The highest critical current of 316 kA cm −2 at 15 K and self‐field was recorded when the liquid phase was infiltrated at 1100 °C. Mahmood et al also reported the J c enhancement in the LIG‐processed Y‐123 superconductors where the pore elimination and Y‐211 refinement was optimized. As a result, the highest critical current density was reported to be 40.4 kA cm −2 at self‐field and 77 K. The combination of the Y‐211 particle size and different configurations of the Y‐123 material obtained the highest J c up to 18 kA cm −2 at 77 K and self‐field .…”

“…The infiltration‐growth (IG) technique involves the infiltration of liquid phase (BaCuO 2 and CuO) into a porous, pre‐solid from of the Y‐211 phase and eventually allowing a reaction between them to form the Y‐123 phase on slow cooling process below T p similar to the melt‐growth experiments . This process allows the fabrication of near‐net‐shaped products, with negligible shrinkage , since an endless supply of liquid phase is provided throughout the texturing process. Furthermore, a uniform microstructure and the refinement of the Y‐211 particles appears to be achieved more effectively without controlling the initially added Y‐211 secondary phase or without refining the Y‐211 particles by Pt or CeO 2 additions due to the self‐refinement of secondary phase particles .…”

“…It was observed that the amount of pores and the secondary phase particle Y-211 size in the final Y-123 matrix were strongly dependent on the pre-form Y-211 density. As a result, the best critical current density observed in high density Y-123 material was 12.2 kA cm À2 at self-field and 77 K [20]. Further, the fabrication of monodomain, bulk Y-123 superconductors has been reported using the IG process and it was found that the secondary phase Y-211 particle size and configuration strongly influences the performance of the final product [21].…”