A safe and cost-effective PMMA carbon source for MgB₂

Carbon is proven to be very effective in pinning the magnetic vortices and improving the superconducting performance of <TEX>MgB₂</TEX> at high fields. In this work, we have used polymethyl methacrylate (PMMA) polymer as a safe and cost effective carbon source. The effects of molecular weight of PMMA on crystal structure, microstructure as well as on superconducting properties of <TEX>MgB₂</TEX> were studied. X-ray diffraction analysis revealed that there is a noticeable shift in (100) and (110) Bragg reflections towards higher angles, while no shift was observed in (002) reflections for <TEX>MgB₂</TEX> doped with different molecular weights of PMMA. This indicates that carbon could be substituted in the boron honeycomb layers without affecting the interlayer interactions. As compared to undoped <TEX>MgB₂</TEX>, substantial enhancement in <TEX>Jc(H)</TEX> properties was obtained for PMMA-doped <TEX>MgB₂</TEX> samples both at 5 K and 20 K. The enhancement could be attributed to the effective carbon substitution for boron and the refinement of crystallite size by PMMA doping.