EFFECT OF MIXING ND, EU, AND GD RARE-EARTH ELEMENTS ON RE-CUPRATE HIGH-T-C SUPERCONDUCTORS

The extent of the relationship between rare earth radius, peritectic d ecomposition temperature (T-p), and lattice dimensions within mixed ra re earth (Nd, Eu, Gd) barium cuprate 123 superconductors has been inve stigated. The peritectic decomposition temperature of compositions wit hin the ''ternary'' (NdxEuyGdz)BazCu3O7-delta (x+y+z=1) material, whil e maintaining a constant average rare earth cationic radius of 1.076 A ngstrom, was observed to be uniform. Powder X-ray diffraction analysis of processed materials also showed the lattice parameters to be unifo rm with these compositional changes. These results indicate a uniform mixing of the RE elements in the RE123 phase. In contrast, the mixing of such RE elements leads to the formation of an inhomogeneous distrib ution of both Nd422 and RE211 second-phase particles in the matrix sub sequent to melt processing.