Effect of laser beam irradiation on the surface of the bulk of press formed superconductor powder

The bulk produced by press forming of superconductor powder never shows sup erconductive characteristics as prepared. The goal of this study is to make superconductive circuits on the surface of the bulk by scanning laser beam . Powder of Bi(Pb) system (2223 composition) was pressed at a pressure of 2 94 kPa to form a 2 mm thick and 10 mm diameter bulk, followed by the irradi ation of a CO2 laser beam by changing output power, scan speed, scan times, and pressure of oxygen as assisted gas. The temperature dependence of elec tric resistance of the resultant specimen was evaluated using the DC four p robe method. The results showed that the resistance around the laser treate d area is as low as 70 m Omega while that of non-treated area is as high as several hundred ohms at room temperature and proved that the laser treatme nt can form a superconductive area having Tc(onset) of 109.5 K (2223 phase) and 81.6 K (2212 phase), and T-c(end) of 66.5 K. (C) 2001 Elsevier Science B.V. All rights reserved.