Narrow Range of Hafnium Doping for Promoted Mechanical Properties and Critical Current Density (J c ) Values of Mg1−x Hf x B2 Superconductor

Abstract

Hafnium was used as a softener dopant to replace at magnesium sites of Mg1−xHfxB2 regime (where x=0.0, 0.05, 0.1, 0.2, and 0.4 mole). Samples were prepared via high temperature solid state reaction technique depending upon diffusion mechanism of Mg-vapor ions through hafnium–boron matrix. The maximum solubility limit of hafnium (n) was found to be ∼0.22 mole. The crystalline lattice constants exhibit slight elongation in the case of the c-axis as x increases. Furthermore, the effect of Hf-doping on the microstructure properties of the MgB2 system was investigated carefully. The SE-microscopic analysis indicated that hafnium ions diffuse regularly through surface and bulk in case of (x=0.05–0.2 mole). The grain size was estimated and found to be between 0.33 and 1.34 μm. The mechanical tensile strength of the samples was clearly improved linearly as Hf-content increased, recording the maximum tensile strength of 34.8 MPa for the sample with x=0.4 mole. A visualization of the Hf-doped MgB2 structure was constructed and investigated to confirm the success of hafnium substitutions at the Mg-sites of the MgB2 superconductor.