Improved J(c) properties of Na-doped MTG YBCO

The effects of Na addition in the MTG YBCO (YBa2-xNaxCu3Oy + 40 mol% Y2BaCu O5) system with x = 0.0, 0.1, 0.2 on T-c and J(c) properties have been inve stigated. It was observed that with increase in x (x less than or equal to 0.2), T-c,T-on is almost the same, but T-c,T-off decreases. With certain Na addition, MTG YBCO showed an improved critical current density characteris tic and a second peak in the magnetization curve. These might be connected with the inhomogeneous distribution of Na, which can become pinning centers against the motion of the flux. The formation of lower T-c phase in Na-ric h region induces the second peak with increasing magnetic fields. (C) 2000 Elsevier Science B.V. All rights reserved.