Preparation and characterization of YBa2Cu3O 7-x thick films deposited on silver substrates by the electrophoretic deposition technique for magnetic screening applications

The production of magnetic shields using high-temperature superconductors (HTS) is not straightforward, as these materials are brittle ceramics. In this paper, we report the results of investigations concerning the use of the electrophoretic deposition (EPD) technique to produce magnetic shields of various shapes and with large surface areas, in the form of a thick coating of HTS on a metallic substrate. For the first time, we report shielding characterization of samples prepared by the EPD technique. The most important problems concern the choice of the process parameters and the heat treatment of the coating, in order to obtain a dense and well-connected polycrystalline system. We have used the HTS compound YBa2Cu3O7-x as the coating material and silver as the substrate. An optimized heat treatment, in an atmosphere with poor oxygen content, was chosen following experimental investigations. Different samples were produced in the form of slabs for chemical, structural and electrical characterization. A cylindrical sample was prepared for magnetic shielding measurements at 77 K. With an applied magnetic field parallel to its axis, the cylinder presents a high level of shielding (>80 dB) at low frequencies, for applied inductions lower than 0.1 mT. If the applied induction is higher than 0.25 mT, the magnetic field inside the cylinder strongly increases. This value is close to the field of penetration given by Bean's model, taking a critical current density of 500 A cm-2 measured by the four-probe technique on similar samples.