Superconducting and Mechanical Properties of the Bulk (SnO2)x(Bi1.6Pb0.4)Sr2Ca2Cu3O10−δ Prepared at Different Sintering Times

Solid-state reaction method was used to prepare superconductor samples with nominal composition of (SnO2)x(Bi1.6Pb0.4)Sr2Ca2Cu3O10−δ, (SnO2)x(Bi,Pb)-2223 composite, where 0.0 ≤ x ≤ 0.2 wt%. The prepared samples were characterized by X-ray diffraction (XRD) as well as scanning electron microscopy (SEM). XRD patterns proved that the addition of nano-SnO2 particles to (Bi,Pb)-2223 did not affect the tetragonal structure and the lattice parameters of this phase. Vickers microhardness measurements (HV) for these samples were carried out at room temperature as a function of applied load, heating temperatures, and dwell time. However, to clarify the indentation size effect (ISE) behavior of these composite materials and to estimate the true microhardness values (H0), different models including Meyer’s law, Hays and Kendall (energy dissipation) model, elastic/plastic deformation model, as well as proportional specimen resistance model were applied. Some important mechanical parameters, such as Young’s modulus (E), yield strength (Y), fracture toughness (K), and brittleness index (B), were estimated from the microhardness curves. It was found that the incorporation of a proper concentration of nano-SnO2 particles has proved their efficiency to enhance the mechanical properties of superconductors. Moreover, it was noted that dwell time and Vickers microhardness were inversely proportional. Indentation creep experiments showed that the operative creep mechanisms in the studied samples were dislocation creep in addition to dislocation interaction.