Vortex pinning in bulk-processed Y–Ba–Cu–O with ZrO2 nano-particles: Optimum pinning center size

Crystalline defects on the nano-scale were successfully introduced into YBCO high-temperature superconductors (HTS) by ZrO2 nanometer particles addition in order to strongly pin the quantized vortices. Three batches of ZrO2 nano-particles with different particle size distributions were used. The corresponding mean nano-particle diameters are respectively, 287, 536 and 764 nm. Serving as artificial pinning centers (APC), non-superconducting nano-particles cause a remarkable enhancement of critical current density (Jc) at T = 77 K. This improvement has been shown to depend on the size of APC. The pinning strength of nano-particles inclusions has been found to be greater with wide size dispersed nano-particles. Our results indicate that pinning properties and vortex dynamics depend on the size of APCs. The introduction of APCs with controlled size is indispensable to achieve a high Jc.

Research highlights
► ZrO2 nanometer particles were added to YBCO in order to pin vortices.
► Three batches of nano-particles with different particle size distributions were used.
► Critical current density improvement is shown to depend on pinning center size.
► Wide size dispersed nano-particles induces stronger vortex pinning.