Optimization of Phase Formation and Superconducting Properties in MgB2 Prepared by Phase Transformation from MgB4

Optimization of sintering conditions in bulk MgB2 material for improvement of critical current density

“…The high T c and the sharp superconducting transition indicate that all sintered MgB 2 samples exhibit good crystalinity and homogeneity. The observed superconducting transition temperatures are similar to the recently reported bulk MgB 2 material fabricated with a solid state reaction method [26]. These results suggest that the superconducting transition temperature of the superconducting matrix in bulk MgB 2 materials is not so sensitive to the variation of the sintering time.…”

“…Fig. 3 shows the critical current behavior of the bulk MgB 2 material at 20 K, sintered for 1 h, 4 h, 5 h, and 10 h at 775 C. It was observed that all samples showed high critical current densities as compared to the recently reported bulk MgB 2 material processed via the solid state sintering method [26]. Note that the highest critical current density of 270,000 A/cm 2 at 20 K and self field was recorded for the samples sintered for 1 h. The critical current density was decreased with increasing the sintering temperature from 1 h to 10 h. These results again clearly demonstrate that the sintering time is crucial to obtain the high critical current density in bulk MgB 2 material.…”

“…The authors concluded that the control of the heat treatment is essential to optimize the weight fraction of the MgB 2 phase, which is in turn essential to improve the critical current density. The highest J c at 5 K and 1 T is around 1 Â 10 5 A/ cm 2 for the sample sintered at 750 C for 4 h [26]. Further, the critical current densities of carbon nanotube doped MgB 2 samples were reported to be higher than 10 4 A/cm 2 at 20 K, 4 T [27].…”

“…The first set of samples were heated to the target sintering temperature of 775 C for 5 h and were held there in flowing argon gas for varying times of 1, 4, 5, and 10 h. Finally, the temperature was lowered to room temperature at a cooling rate of 100 C/h. The second set of samples were prepared using the normal B (purity 99.99%, 300 mesh) powders in which is similar to the privies of our reports [26]. In the second set, the samples were heated similarly to the first set, i.e., in 5 h to reach the sintering temperature, which was varied between 775 C and 805 C in steps of 5 C. At the sintering temperature, the temperature was kept constant for 3 h in flowing argon gas.…”

Effects of the size of Mg powder on the formation of MgB2and the superconducting properties

“…In the reaction process using MgB 4 and Mg powders, the amount of Mg used to form MgB 2 is smaller than the conventional in situ process [21][22][23]. Therefore, the number of pores can be reduced.…”