Preparation of superconductive layer on the press formed bulk from Bi system superconductor powder by laser irradiation

A study on the preparation of superconductive layer on the press formed bulk from Bi system superconductor powder by laser melting method was conducted. Pulverized and filtered with a net of 325 mesh superconductor powder of the system was pressed to form a bulk of 2 mm thick and 10 mm diameter disk. The bulk specimen showed no superconductive characteristics as formed. Then, a CO2 laser beam of output power 6-9 W was scanned at 2 or 10 mm/min on the surface of the specimen in the air. This laser treatment yields gradual change in temperature from the melting point to the non-heat-affected temperature range on the surface and inside the bulk. The influence of the specimen forming pressure on the critical temperature was also discussed. It was found that (1) surface layer laser melted shows the characteristics of semiconductor, (2) superconductor layer is formed underneath the melted layer, i.e., semiconductor layer, (3) this superconductor layer prepared mainly consists of mainly 2212 phase, (4) the thickness of superconductor layer can be controlled in the range between 60 and 130 μm by changing output power, and (5) the critical temperature of Tc(end) is influenced by laser treatment conditions as well as the pressure to form the bulk specimen