Transport properties of the rare earth disordered systems (R/sub 1-x/Yb/sub x/)Ba/sub 2/Cu/sub 3/O/sub 7/ (R = Y, Sm)

Electrical and magnetic measurements have been carried out for the rare earth disordered superconducting copper oxide systems (Y/sub 1-x/Yb/sub x/)Ba/sub 2/Cu/sub 3/O/sub 7/ (substitution with large rare earth mass difference) and (Sm/sub 1-x/Yb/sub x/)Ba/sub 2/Cu/sub 3/O/sub 7/ (substitution with large rare earth ionic size difference). Effect of compositional variation upon room temperature electrical resistivity shows no disorder scattering contribution from the randomly distributed rare earth ions located on the (1/2, 1/2, 1/2) site of the space group Pmmm. This result indicates very low conduction electron density of states surrounding rare earth ions. On the contrary, negative deviation of electrical resistivity from the linear Vegard law was observed. This reduced conduction electron scattering was discussed through the variation of packing density, grain size and/or twin structure.