Synthesis, structural aspects and superconductivity of La1-xRExBaCaCu3O7 with RE=Nd, Dy, Sm and Pr

We have investigated the structural aspects and superconductivity of La1-xRExBaCaCu3O7 system in detail, with the help of X-ray diffraction and magnetic susceptibility studies. While a complete substitution of Nd and Pr takes place isostructurally in La:1113 (LaBaCaCu3O7) compound, for Dy and Sm, both are only partial, namely, it is 50 at.% for the former and 75 at.% for later. Unlike the RE:123 system, in the presently studied RE:1113 compound, the phase formation and onset T-c an both strongly dependent on the chosen rare earth (RE). Pr has a less deleterious effect on the superconductivity of La:1113 system than that reported for La:123. These results of phase formation and the different T-c values for various rare earths are discussed on the basis of interesting structural chemistry of this compound, which involves the intermixing of RE, Ba and Ca sites in RE:1113 compounds. (C) 1998 Elsevier Science B.V. All rights reserved.