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Instantaneous high temperature improved the low-temperature sintering efficiency of the un-doped MgB 2 superconductor, and the MgB 2 was rapidly synthesized at 600 °C for only 2 h. In addition to the refinement of MgO impurity particles, the sudden high temperature induced defects within the MgB 2 grains, e.g. twinning crystal, and the J c performance is therefore significantly enhanced, about 2.2 × 10 3 A·cm − 2 at 4 T for bulk sample. Differed from the two-dimensional nucleation growth mode of the MgB 2 grains in the high-temperature sintered un-doped sample, the low-temperature sintered MgB 2 grains accord with the dislocation growth mechanism, relying on the thermal-stress-triggered twinning crystal. [ABSTRACT FROM AUTHOR]

Sintering temperature plays a vital role in the evolution of phase structure and microstructure in polycrystalline FeSe 0.5 Te 0.5 bulks fabricated by the two-step sintering method, and thus significantly influences their superconducting properties. Elevated sintering temperature (600–700 °C) at second step facilitates the substitution of Te into the superconducting phase, which leads to the increased lattice distortion and thus contributes to the enhancement of superconductivity (the value of T c reaches 15.6 K). At the same time, the accelerated growth of the superconducting grains and the improved homogeneity motivated by elevated sintering temperature serve as the main reason for the sharp superconducting transition. [ABSTRACT FROM AUTHOR]

Lamellar MgB2 grains were synthesized by Cu-activated sintering at low temperature. We found that the Mg–Cu liquid can provide a constant liquid environment and the formation of lamellar MgB2 grains is attributed to the two-dimensional nucleation and growth mechanism in the liquid–solid interface. According to the analysis on the temperature dependence of resistivity, these lamellar MgB2 grains possess much better grain connectivity than the typical morphology of MgB2 grains synthesized by the traditional solid-state sintering. [Copyright &y& Elsevier]

Multi-doped MgB2 superconductors with excellent critical current density (Jc ) were rapidly synthesized by low-temperature activated sintering with Cu addition as the activator and nano SiC addition as the carbon-based chemical. Combined with microstructure observation and flux pinning force analysis, it is found that the enhancement of Jc (especially at low field) was mainly attributed to the higher density, lower crystallinity and the concentration of Cu activator around the sintered voids. [Copyright &y& Elsevier]