A class of chemical pinning centers including two elements foreign to HTS

Very small deposits are formed when two foreign elements, A and B, are added to textured (RE)BCO. These deposits increase the J(c) of samples and hence the maximum trapped field. Deposit sizes are generally in the range 200-400 nm. Their chemical composition is (A(x),B-y)(RE)Ba2O6, where x + y = 1 and x = y +/- 0.1. Their structure is double perovskite. The deposits produce two types of pinning, one by refinement (e.g., of the Y211 phase) and the other due to the double perovskite deposits themselves. In those cases tested, the refinement increases J(c) by factors exceeding 1.33, and the deposits increase J(c) by factors exceeding 2, for a total increase by a factor exceeding 2.66. Element A can be U, W or Mo. Element B can be Pt or Zr. We speculate on possible additional elements in classes A and B. (C) 2002 Elsevier Science B.V. All rights reserved.