Investigation on superconducting properties of GdBa sub(2)Cu sub(3)O sub(7 - delta ) added with nanosized ZnFe sub(2)O sub(4)

• Published in: Journal of alloys and compounds 2014-10, Vol.610, p.614-622
• Main Authors: Awad, R, Aly, A I Abou, Mohammed, N H, Isber, S, Motaweh, H A, Bakeer, D El-Said
• Format: Article
• Language: English
• Subjects: Electrical resistivity; Hysteresis; Magnetic permeability; Nanostructure; Scanning electron microscopy; Superconductivity; Vickers microhardness; X-ray diffraction
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2014.05.005

The effect of nanosized ZnFe sub(2)O sub(4), prepared by Co-precipitation method, on GdBa sub(2)Cu sub(3)O sub(7 - delta ) superconductor was studied. Therefore, superconducting samples of type (ZnFe sub(2)O sub(4)) sub(x )GdBa sub(2)Cu sub(3)O sub(7- delta ), 0.0 [< or =, slant] x [< or =, slant] 0.1 wt.%, were prepared by the conventional solid-state reaction technique. Moreover, nanosized ZnFe sub(2)O sub(4) was characterized using X-ray powder diffraction (XRD), transmission electron microscope (TEM) and magnetic hysteresis measurements. The results revealed that a nanosized ZnFe sub(2)O sub(4) was achieved with average grain size 9 nm and a super-paramagnetic hysteresis. On the other hand, the superconducting samples were characterized and investigated through XRD, scanning electron microscope (SEM), electrical resistivity, ac magnetic susceptibility and Vickers microhardness. XRD results showed that the volume fraction of Gd-123 phase increases as x rises from 0.0 to 0.06 wt.% while the SEM results showed that the grain connectivity between the grains increases with increasing x. The superconducting transition temperature T sub(c) determined from electrical resistivity and ac magnetic susceptibility, increases up to x = 0.06 wt.%, and then it decreases. Moreover, electric field-current density (E-J) characteristic curves were measured at 77 K. An improvement of the critical current density was obtained with x increase up to 0.06 wt.%. Furthermore, the Vickers microhardness data were analyzed using Meyer's law, Hays-Kendall approach, elastic/plastic deformation model and proportional specimen resistance model. The results indicated that Vickers microhardness number H sub(v)increases as x increases and it exhibits a normal indentation size effect. Moreover, the proportional specimen resistance model is found to be the best model to verify the experimental load independent Vickers microhardness values.