Flux pinning characteristics of YBCO: NaNbO3 by introducing artificial pinning centers with different morphology

Introduction of artificial pinning centres in different morphology is a beneficial way to improve the flux pinning properties of a YBCO compound. In the present study, we report the effect of addition of sodium niobate (NaNbO3) nanostructures in two different form i.e. nanorods (NRs) and nanoparticles (NPs) with a varied wt% (0, 0.5, and 1 wt%) on the pinning capabilities of bulk YBCO polycrystalline samples. The orthorhombic crystal structure of YBCO was confirmed by the XRD spectra even in the nanocomposite samples. The existence of NPs or NRs on the surface and between the superconducting grains of YBCO was confirmed by morphological analysis. The critical temperature (Tc) remains almost unchanged as compared to pure YBCO on addition of NaNbO3 nanostructure in YBCO compound upto 1 wt% concentration. Even at higher fields (upto 6 T) and higher temperatures (upto 75 K), the addition of NaNbO3 NPs or NRs in YBCO nanocomposite resulted in a significant increase of similar to 2.6 times in the critical current density as compared to pure YBCO. In comparison to NRs added YBCO nanocomposite samples, NPs added YBCO nanocomposite samples showed higher improvement. Throughout the entire investigated range of applied field, the maximum pinning force was found for 0.5 wt% NPs added composite sample.