Enhanced Critical Current Density in MgB2 Superconductor via Si and C Coadditions

Abstract

In this study, nanosize Silicon and Carbon (Si+C) were reacted with MgB2 in order to enhance the critical current density. The polycrystalline bulks were synthesized by the direct in situ reaction method and their phase formation, crystal structure, and superconducting properties were evaluated. The enhanced relative peak intensity of Mg2Si and MgB4 indicates the formation of a large volume fraction of these two phases with increasing (Si+C) additions. The a-axis lattice parameter shrinks significantly while c-axis increases slightly. The estimated C doping level at B site increases, leading to a degradation of the superconducting transition temperature with increasing (Si+C) additions. By a reaction with (Si+C), the field dependence of critical current density is shown to enhance at both 5 K and 20 K.

Reaction method control of impurity scattering in C-doped MgB2: proving the role of defects besides C substitution level

“…For comparison, another set of samples were prepared in a similar way using 3.0 wt% of individual silicon and carbon (Si + C) nano-powders. Samples reacted with 3.0 wt% SiC and Si + C were chosen for the present study because they have a high critical current density [24]. Undoped MgB 2 pellets were also prepared as control samples.…”

“…For the pure sample sintered at 650 • C, the calculated relative intensity fraction [24] for MgO is 4.6% compared with 8.5% for the sample sintered at 850 • C (table 1), indicating the latter was oxidized more severely. As shown in table 1, the calculated relative intensity fraction of Mg 2 Si for the samples sintered at 650 • C is larger compared with that of the samples sintered at 850 • C. This is expected based on the fact that Mg 2 Si has a more negative Gibbs energy of formation at the lower temperature (−71.3 kJ mol −1 at 900 K compared with −65.7 kJ mol −1 at 1100 K) [27], thus making it form more easily.…”

Synthesis of Bulk FeTe1−x Se x (x = 0.1−0.5) at Ambient Pressure

“…In addition, powder handling was done in air. Previously, this method has been widely used for preparing MgB 2 superconductor ( [18] and references therein). Our attempt is to establish an inexpensive and yet simple method in preparing FeTe 1−x Se x .…”

Enhanced critical current density of ex situ MgB2 via control of Mg assisted sintering

“…Looking at Table 1, the values of the a-and c-axis are comparable for the samples with a higher and lower amount of MgO and MgB 4, suggesting the negligibly small influence of these phases on the lattice parameters. Intensity fractions of the phases formed were estimated using the formula [30][31][32]:…”