Effect of hard magnetic ferrite (Ba0.5Sr0.5Fe12O19) nanoparticles on the mechanical properties of the (Bi, Pb)-2223 phase

Abstract

Abstract To manifest the effect of hard magnetic Ba 0.5 Sr 0.5 Fe 12 O 19 nanoparticles on the mechanical performance of the (Bi,Pb)-2223 superconducting phase, nano-(Ba 0.5 Sr 0.5 Fe 12 O 19 ) x /Bi 1.8 Pb 0.4 Sr 2 Ca 2 Cu 3.2 O 10+δ , with x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.10, and 0.20 wt%, were synthesized using a conventional solid-state reaction method. The X-ray diffraction (XRD) data revealed that adding nano-(Ba 0.5 Sr 0.5 Fe 12 O 19 ) to the host (Bi,Pb)-2223 phase preserved the orthorhombic structure. The porosity ( P %) calculations revealed a decrease until x = 0.04 wt%, which suggests that the addition of nano-(Ba 0.5 Sr 0.5 Fe 12 O 19 ) x reduces the number of voids and improves inter-grain connections, as confirmed by SEM micrographs. The superconducting transition temperature ( T c ) increased to 112 K with the inclusion of nano-(Ba 0.5 Sr 0.5 Fe 12 O 19 ) up to x = 0.04 wt%. Vickers microhardness ( H V ) measurements were conducted at various applied loads (0.245–9.800 N) and a duration time of 45 s. The H V number increased with the addition of x up to x = 0.04 wt% but then decreased with further addition. Various models were employed for analysis and modelling of Vickers hardness ( H V ) versus test load (F), including Meyer’s law, Hays–Kendall (H–K) model, the elastic/plastic deformation (EPD) model, the proportional sample resistance (PSR) model, the modified proportional sample resistance (MPSR), and indentation-induced cracking (IIC) model. It was found that the PSR model was the most appropriate theoretical model for describing the microhardness of nano-(Ba 0.5 Sr 0.5 Fe 12 O 19 ) x /(Bi,Pb)-2223 composites. Moreover, the elastic modulus ( E ), yield strength ( Y ), fracture toughness ( K ), brittleness index ( B ), and elastic stiffness coefficient ( C 11) were estimated as a function of the inclusion of nano-(Ba 0.5 Sr 0.5 Fe 12 O 19 ) x . Furthermore, the indentation creep test (time-dependent Vickers microhardness) revealed that the dislocation creep mechanism exists in composite samples with low concentrations ( x < 0.05 wt%), whereas the dislocation climbs creep mechanism was observed for x ≥ 0.05 wt%.