Improvement of mechanical properties of YBCO-Ag composite superconductors made by mixing with metallic Ag powder and solution

Abstract

The role of Ag additions in the microstructural evolution and related mechanical properties of YBCO has been studied. Various amounts of Ag have been added to YBCO by two different mixing techniques, i.e. in the form of metallic Ag powder and solution. The strength and fracture toughness of YBCO specimen increased with increasing Ag content, probably because of strengthening mechanisms resulting from Ag addition. In addition, YBCO-Ag composites showed higher values of strength and fracture toughness when Ag was added in the form of solution compared with those when it was added in the form of metallic Ag powder. Specifically, an addition of 10 vol% Ag, made by mixing with metallic Ag powder, increased strength from 88 to 116 MPa and fracture toughness from 1.6 to . Corresponding improvements in strength and fracture toughness were 128 MPa and , respectively, when YBCO was mixed with solution. The better mechanical properties of the YBCO-Ag specimen mixed by the solution method are believed to be due to the microstructure of more finely and uniformly distributed Ag particles. Furthermore, addition of Ag did not have an adverse effect on the critical current density of YBCO superconductors.

Conductivity fluctuations of polycrystalline Ag-doped YBa2Cu3O7-δ superconductor

“…Figure 7 shows the inverse of the logarithmic derivative of the conductivity, χ −1 σ , as a function of temperature for GD sample (J = 800 mA/cm 2 ). The maximum of dρ/dT is signaled and can be observed a set of fluctuation regimes labeled by λ (1) cr , λ (2) cr , λ 1 (all observed above T P ) and s (observed between T CO and T P ). The exponent λ 1 = 0.55 ± 0.03 corresponds to homogeneous 3D fluctuations while the exponent λ (2) cr = 0.32 ± 0.03 characterizes the asymptotic regime precursor to the pairing transition, and consistent with the 3D − XY model [22].…”

“…In Figure 5 we show the resistive transition of GB sample. The measurement was performed with a current density of 800 mA/cm 2 T results is plotted. The zero resistance temperature, T C0 , is achieved at approximately 91 K, and we can observe that T P ∼ = 93 K. Also, we can identify the temperature interval relevant for studying fluctuations in the normal phase (above T P ) and the regime dominated by mesoscopic granularity (close to the ρ = 0 state) [19].…”

“…Numerous studies have shown that Ag-doping of YBa 2 Cu 3 O 7−δ superconductors results in improved superconducting properties in bulk samples [1][2][3][4][5], as for example, the mechanical properties of melt-textured YBCO [3,5]. Also, as Ag fills the intergranular spaces, it improves the electrical properties of the samples, enhancing the critical current density without changing the superconducting transition temperature T C [6].…”

Magnetical Response and Mechanical Properties of High Temperature Superconductors, YBaCu3O7-X Materials

“…The fracture toughness of YBa 2 Cu 3 O 7-x melttextured samples has been determined by Vickers indentation (Leblond-Harnois et al, 2000; Li et al, 1997;Yoshino et al, 2001;Cook et al, 1987;Fujimoto et al, 1992), and also by the single-edge notch beam (Joo et al, 1998) and bending (Giese et al, 1990) techniques. Values in the range of K IC =0.4-2.8 MPa·m 1/2 have been found, with a scattering attributed to differences between the techniques employed to obtain this parameter.…”

“…In addition, K IC is influenced by exact matrix composition. For instance, Joo et al (Joo et al, 1998), reported that the fracture toughness of YBa 2 Cu 3 O 7-x increased from K IC =1.60 MPa·m 1/2 to 2.80 MPa·m 1/2 by adding a 15% in volume of silver to the matrix.…”