Structure and transport studies on nanometer YBCO/PBCGO multilayers

We have fabricated M doped (M = Al, Co, Fe, Ga, Ni and Zn) PrBa2Cu3O7 (PBCO), i.e. PrBa2(Cu1-xMx)3O7. The doping levels x are 0.05, 0.10, 0.15, and 0.20. X-ray data indicated no significant second phase for substituting Cu by Al, Co, Fe and Ga up to 20%. However impurity phases were detected for Ni and Zn substituted samples with doping levels equal to and higher than 15%. At 77 K the electrical resistivity of these compounds is orders in magnitude higher than that of PBCO. We also found that although the lattice parameters in the doped samples differ from PBCO, all samples remain orthorhombic. The lattice parameters of the doped sample are very close to those of YBa2Cu3O7-δ (YBCO) and PBCO. For this reason these compounds are better materials to be used as the I-layer for YBCO SIS junctions. Results of structural and transport studies on 2000 thick PrBa2[Cu0.80G0.2]3O7 (PBCGO) and YBCO/PBCGO multilayers are presented in this paper.