W. Abdeen

Electrical and mechanical properties of (Bi,Pb)-2223 substituted by holmium

The effect of the partial substitution of Ca2+ by Ho3+ ions on the electrical and mechanical properties of the superconducting phase (Bi,Pb)-2223 was studied. Superconducting samples of the type (Bi1.8Pb0.4)Sr2Ca2.1−xHoxCu3.1O10+δ were prepared by solid-state reaction technique under ambient pressure, and characterized by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The superconducting transition temperature Tc and pseudogap temperature T* were estimated from electrical resistivity measurements, while the critical current density Jc was determined from I–V curves. The electrical resistivity data were discussed according to bipolaron model in the absence of thermally excited individual polarons. The sample with x = 0.025 showed the highest phase volume fraction, Tc, and Jc. Room temperature Vickers microhardness measurements were carried out at different applied loads (0.25–5 N) in order to investigate the performance of the mechanical properties of (Bi1.8Pb0.4)Sr2Ca2.1−xHoxCu3.1O10+δ phase. It was found that all the samples exhibit normal indentation size effect (ISE). The Vickers microhardness number HV increased as x increased from 0 to 0.025. The experimental results were discussed in view of Meyer’s law, Hays–Kendall (HK) approach, elastic/plastic deformation (EPD) model, and proportional specimen resistance (PSR) model. The load independent (true) microhardness of (Bi1.8Pb0.4)Sr2Ca2.1−xHoxCu3.1O10+δ superconducting samples showed identical behavior to that of the PSR model.

Electrical resistivity behaviour in Tl2Ba2Ca1−xRxCu2O8−δ with R = Nd and Gd

The effect of the partial substitution of Nd3+ and Gd3+ ions on the electrical resistivity of Tl2Ba2CaCu2O8−δ is studied. Superconducting samples of the nominal composition Tl2Ba2Ca1−xNdxO9−δ (0 ≤ x ≤ 0.6) and Tl2Ba2Ca1−xGdxCu2O8−δ (0 ≤ x ≤ 0.4) are prepared under normal pressure using the one-step solid-state reaction technique. The prepared samples are characterized and investigated using x-ray powder diffraction, scanning electron microscopy and electrical resistivity. The x-ray data clarify that the replacement of the Ca2+ ion by Nd3+ and Gd3+ ions does not influence the tetragonal structure of the pure sample and the lattice constants vary according to the type and content of the substitutional ions. The transition temperature, TC, determined from the electrical resistivity data, shows a depression in its values as the substitutional content increases. We discuss possible reasons for the suppression in the superconductivity of the system studied.

Erratum to: Electrical and mechanical properties of (Bi,Pb)-2223 substituted by holmium

Erratum to: Electrical and mechanical properties of (Bi,Pb)-2223 substituted by holmium W. ABDEEN, S. MARHABA, R. AWAD, A. I. ABOU ALY, I. H. IBRAHIM, M. MATAR Superconductivity and Metallic Glass Lab, Physics Department, Faculty of Science, Alexandria University, Alexandria, Egypt Physics Department, University College at Al-Gamom, Umm Al-Qura University, Saudi Arabia Physics Department, Faculty of Science, Beirut Arab University (BAU), Beirut, Lebanon