Preparation of High-Tc Superconducting Magnetic Shields by a Low Pressure Plasma Spraying

Abstract

A perfect magnetic shielding can be achieved by superconductors, because the magnetic flux can not penetrate into superconductors at magnetic field of less than their lower critical magnetic field; Hc1, (Meissner effect). Thus, the superconducting magnetic shields are much advantageous for biomagnetic and other applications whereby an absolute minimum of magnetic background noise is required. However, metallic superconductors such as Nb or Nb-Ti require a cooling by liquid helium. Meanwhile, the high-Tc oxide superconductors developed recently have critical temperature (Tc) over liquid nitrogen temperature. For example, YBa2Cu3O7-x 1) has Tc of 90K. Therefore, oxide superconductors enable the operation of the sperconducting shields at more practically favorable liquid nitrogen temperature. We have developed a low pressure plasma spraying technique for the deposition of YBa2Cu3O7-x superconductor thick film2. This technique facilitates the deposition of dense YBa2Cu3O7-x films on the substrate with complicated shapes and large areas at a high deposition rate. Thus, a low pressure plasma spraying has a great advantage to fabricate magnetic shields with thick films of oxide superconductor.