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Four Ge-based organometallic (OM = C6 H10 Ge2O7 ) polymers with similar chemical composition were used as additions for MgB2. MgB2 (OM)0.0014 dense samples with a relative density higher than 97% were obtained by ex situ spark plasma sintering. The critical current density and the irreversibility magnetic field of the added samples are slightly improved at highmagnetic fields by repagermanium (Alfa Aesar) addition when compared to the pristine reference sample. Addition ofGe-straightchain polymer shows some improvement of the maximum volume pinning force, Fp max . There is no significant Ge substitution in the crystal lattice of MgB2, while C substitutes for B. Pinning mechanism is mainly of a point pinning type, with the grain boundary pinning mechanism strengthening at lower temperatures and when additives are not used. A relatively high amount of carbon in the samples washes out the Ge effects on pinning-force-related parameters. The structure and morphology of the polymer additive play an important role in dispersion whenmixing, impacting the quality of the superconducting properties. The nanosize dimension of the pristine MgB2 powder shows also some drawbacks in mixing and sintering. [ABSTRACT FROM AUTHOR]

Infiltration growth (IG) process is superior compared to the conventional melt growth technique and is susceptible to various parameters. In this work, we had optimized the amount of Dysprosium (Dy) in top-seeded IG processed bulk hightemperature GdBa2Cu3O7-δ (GdBCO) superconductors for an enhancement of flux pinning. Similar sized 0, 10, 20, 30, and 40 wt% of the Dy2BaCuO5 secondary phase particles were added in Gd2BaCuO5 preforms, which were further subjected to topseeded IG process in an air atmosphere. The microstructural and magnetic properties of (Gd, Dy)BCO superconducting systems were evaluated. The Dy addition shows no major influence on the microstructural features, but strongly indicates enhanced magnetic properties of final bulk (Gd, Dy)BCO composites. Sharp superconducting transitions were observed for all samples with an onset of critical temperature of~93 K. The critical current density Jc of 45.5 kA/cm2 was achieved at self-field and 77 K in optimized composition of 20 wt% Dy-added GdBCO superconductor, and a considerable Jc of 20 kA/cm2 was observed at an applied magnetic field of 2 T. The enhancement in superconducting properties was ascribed to a distribution of optimized stress fields induced by lattice mismatch defects and chemical compositional fluctuations. [ABSTRACT FROM AUTHOR]

In a quench event determined by instability of the flux-flowregime, the quenching current I* can be much higher than the critical current Ic; thus, it sets the upper limit to the superconducting operational regime. In iron-based Fe(Se,Te) superconducting thin films, which can be relevant to fabricate conductors for high magnetic field applications, substantial differences between the Ic and I* behavior as a function of the applied magnetic field have recently been observed. Both current values are strongly influenced by flux pinning; thus, anisotropy effects are expected to play a role. Here, we report the first study of the angular dependence on themagnetic field orientation of the quenching current in Fe(Se,Te) thin films grown on a CaF2 substrate, which have already shown a weak anisotropic critical current dependence on the applied magnetic field orientation. The quenching current is found even less sensitive than the critical current with respect to angular variations. [ABSTRACT FROM AUTHOR]

Four Ge-based organometallic (OM = C6 H10 Ge2O7 ) polymers with similar chemical composition were used as additions for MgB2. MgB2 (OM)0.0014 dense samples with a relative density higher than 97% were obtained by ex situ spark plasma sintering. The critical current density and the irreversibility magnetic field of the added samples are slightly improved at highmagnetic fields by repagermanium (Alfa Aesar) addition when compared to the pristine reference sample. Addition ofGe-straightchain polymer shows some improvement of the maximum volume pinning force, Fp max . There is no significant Ge substitution in the crystal lattice of MgB2, while C substitutes for B. Pinning mechanism is mainly of a point pinning type, with the grain boundary pinning mechanism strengthening at lower temperatures and when additives are not used. A relatively high amount of carbon in the samples washes out the Ge effects on pinning-force-related parameters. The structure and morphology of the polymer additive play an important role in dispersion whenmixing, impacting the quality of the superconducting properties. The nanosize dimension of the pristine MgB2 powder shows also some drawbacks in mixing and sintering. [ABSTRACT FROM AUTHOR]