Effect of Ball Milling Time on Critical Current Density of Glucose-Doped MgB2 Superconductors

Abstract

The planetary ball milling (BM) is extensively used in synthesizing the bulk MgB2 samples owing to its flexibility of operation, the ease of usage, and a faster mixing and is easy to scale up. The effect of ball milling time (BMT) on the physical parameters is investigated here to get the optimum time of BM in order to have better JC(H,T) in MgB2. Lattice parameters, critical current density (Jc), and resistivity (ρ) of MgB2 samples doped with 2 % of glucose (C6H12O6) prepared by different BMT mixing are investigated here. Four different samples of Mg (B.98C.02)2 were prepared using in situ solid state reactions of magnesium (Mg), boron (B), and glucose in stoichiometric ratio at 2, 4, 8, and 12 h using planetary ball milling. A reference sample of undoped MgB2 was also prepared under the same conditions at an 8-h BMT. The a-lattice parameter is reducing up on increasing BMT and getting saturated at 8 h. Similarly, TC is decreasing with the increase of BMT and saturates at 8 h. The critical current density JC(H,T) of all samples was calculated from the M-H loop measurements, and it shows that the value of it is the highest in an 8-h BMT sample in comparison to that of all other samples. At 5 K, JC of 104 A/cm2 value in 8.2T is achieved, and at 20 K, the JC value of 104 A/cm2 in 4T is achieved. The better performance of an 8-h BM sample is due to the better dispersion of glucose and hence the uniform substitution of C in MgB2 at an 8-h BMT.