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Highlights: [•] The effect of nanosized ZnFe2O4 on the Gd-123 phase was studied. [•] The phase formation and superconducting parameters were improved up to x =0.06wt.%. [•] The Vickers microhardness number increased as x increased. [•] The Vickers microhardness data agreed with the proportional specimen resistance model. [ABSTRACT FROM AUTHOR]

Vickers microhardness measurements of Y 3−x Nd x Ba 5−x Ca x Cu 8 O 18−δ samples, 0.00 ≤ x ≤ 0.40, were carried out at room temperature at different applied loads varies from 0.25 N to 10.00 N. Vickers microhardness decreases as the substitution content increases, as well as it decreases as the applied loads increase. The results were analyzed using different models such as Meyer's law, Hays–Kendall (HK) approach, elastic/plastic deformation (EPD) model, proportional specimen resistance (PSR) model and modified proportional specimen resistance (MPSR) model. The analysis shows that the MPSR model is the most suitable one to describe the load independent microhardness for Y 3−x Nd x Ba 5−x Ca x Cu 8 O 18−δ superconducting samples at high load. Some important mechanical parameters such as Young's modulus ( E ), yield strength ( Y ), fracture toughness ( K f ) and brittleness index ( B i ) were calculated as a function of substitution content. The results show that they decrease by increasing the substation content for Y 3−x Nd x Ba 5−x Ca x Cu 8 O 18−δ samples. [ABSTRACT FROM AUTHOR]