Fabrication and characterization of ethylcellulose-based polymeric magnesium diboride superconducting tapes

Magnesium diboride was found to be a simple intermetallic superconductor in 2001 with the highest critical temperature to date at 39 K. Following this discovery thousands of studies have been conducted into the synthesis and modification of this simple binary compound. Additionally, magnesium diboride has been studied in order to understand the fundamental physics of superconductivity. However, implementation of commercial applications has been limited due to the associated difficulty of production. The compound itself is relatively cheap to produce however, standard powder-in-tube methods for wire production require multiple steps and could prove to be difficult to incorporate into automated production.;All samples produced with this new method were found to be superconductive. Results from transport measurements in normal atmosphere (1000 mbar) and magnetization measurements revealed a transition temperature of 37.5 K +/- 0.7 K. The critical current and critical current density were very low for all samples, measured at most to be 4.21x10-3 A and 1.85x10-1 A/cm2. The upper critical magnetic field at 4.2 K was as high as 6.38 T for the best tapes and the lower critical magnetic field was 0.27 T. The transport properties were found to be strongly dependent on the pressure of the helium atmosphere surrounding the samples. The normal resistance improved at low pressure.;These tapes, produced using a wet and dry mixing method, were superconductive and easy to produce and demonstrate that superconductivity persists in a composite two-phase material. However, the low critical current density points to the presence of many Josephson junctions. No vortex motion was observed and implies strong pinning forces probably due to the polymer component which restricts vortex motion.;In this thesis project, two-phase superconductor tapes were produced by blending high purity magnesium diboride powder with a liquid ethylcellulose-based polymeric binder and simply leaving them to dry. Shaping the tapes required a simple cutting tool and some peeling from the flexible aluminium substrate. The objective was to produce robust, superconductive coatings which can potentially be shaped into any geometry including wires and tapes without necessitating sintering and pressing steps for eventual commercial applications. The transition temperature as well as the critical fields were determined using electrical transport and magnetization measurements. Fourier-transform infrared spectroscopy using a photoacoustic cell was used to determine the normal state vibration modes of the two main components, MgB2 and ethylcellulose, in the superconducting tapes.