JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, vol.35, no.10, pp.2737-2748, 2022 (SCI-Expanded)
A systematic study was reported on the effect of the sintering temperature on the bulk electromagnetic properties, such as levitation force, trapped field and flux pinning mechanism of bulk MgB2, via both experimental and numerical methods. Disk-shaped MgB2 pellets were manufactured using in situ sintering technique at temperatures ranging from 700 to 850 degrees C in pure Ar atmosphere. The sample sintered at 700 degrees C shows higher J(c) values at the magnetic fields above 0.68 T, indicating changing pinning centre density and thus pinning behaviour of the samples by different sintering temperatures. The levitation force and guidance force values increase with increasing sintering temperature from 700 to 775 degrees C and then decrease for the sample sintered at 850 degrees C. At higher fields, the bigger pinning force density of the sample sintered at 700 degrees C can be attributed that the Mg particles are more effective to act as pinning centres inside the MgB2 sample than that of MgO particles at higher magnetic field region of about 0.7 T. The consistency of numerical trapped flux values with the J(phi) bulk supercurrent density inside the samples and the experimental trapped flux results in literature indicates the success of the numerical modelling performed in this study. Two types of pinning mechanism for high- and low-field regions were determined for pure MgB2 samples. The experimental results of this study clearly show that the optimum sintering temperature is an effective process to obtain high levitation capability and trapped field in especially pure bulk MgB2 material. It can be additionally said that the numerical results are useful to understand the physical background of the intrinsic pinning mechanism in pure MgB2 and so to fabricate tailored doped MgB2 superconducting samples with enhanced electromagnetic properties.