Journal of Advanced Ceramics


(Bi, Pb)-2223 phase, Ho substitution, Vickers microhardness, bipolaron model, pesudogap temperature


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.


Tsinghua University Press