A superconductive shielding can for high Tc SQUID

The authors have fabricated yttrium-barium-copper-oxygen ceramic superconductive shielding cans and measured the magnetic shielding properties at liquid-nitrogen temperature by using a Hall magnetic sensor and high-T_c SQUID (superconducting quantum interference device). They report the fabrication processing of the shielding cans and the measurement results. The magnetic properties of the bulk samples are very different from those of conventional superconductors. There are lots of grain boundaries and defects inside the ceramic samples. The magnetic field can penetrate through those defects into the sample easily. The physical density of the samples is of great importance for their superconductive magnetic shielding ability. The isostatic pressing technique, which has been used in this work to prepare a dense and uniform cylinder, is a key processing method