Improved flux pinning in PMP YBa2Cu3Oy superconductors by submicron Y2BaCuO5 addition

YBa2Cu3Oy samples with varying Y2BaCuO5 (211) second-phase concentrations have been prepared using the submicron-sized 211 precursors by a powder melting process method and their critical current density (J(c)), flux pinning and microstructure have been investigated. The microstructural observations show that most 211 particles in the sample are submicron in diameter (as small as 300 nm), which can work as effective pinning centers. J(c) in low fields increases monotonously with increasing the 211 concentration. A high irreversibility field above 7 T at 77 K in H\\c is observed in these samples. A very high J(c) value of 1.6 x 10(5) A/cm(2) at 77 K in self-field has been achieved in the sample with 25% 211 addition. A plateau-region of J(c) versus field (as high as 60 000 A/cm2 at 77 K) is also obtained, which is very promising for applications. In addition, the scaling of pinning force as a function of the reduced field gives a peak position of 0.33 which is an indication of pinning provided by normal conducting 211 particles. (C) 2002 Elsevier Science B.V. All rights reserved.