PrBa₂[Cu_1-xM_x]₃O₇ AS I-LAYER MATERIALS FOR JOSEPHSON SIS JUNCTIONS

Abstract

Metal (M) doped PrBa 2 Cu 3 O 7, i.e. PrBa 2( Cu 1-x M x)3 O 7 for M = Al , Co , Fe , Ga , Ni and Zn , and x =0.05, 0.10, 0.15, and 0.20 were fabricated. No significant second phase was found for the Al , Co , Fe and Ga doped samples up to 20% doping level. Impurity phases, however, were detected for Ni and Zn doped samples when doping concentration reached 15% and higher. At 77 K the electrical resistivity for most of these compounds is several orders in magnitude higher than that of the PrBa 2 Cu 3 O 7-δ. Although the lattice parameters in the doped samples changes toward tetragonal structure, all sample remained in orthorhombic structure and the parameters remain very close to those of the undoped one and YBa 2 Cu 3 O 7-δ. For this reason these compounds may serve as improved I-layer materials for making YBa 2 Cu 3 O 7-δ SIS Josephson junction.

Finite Size Effect on Ybco/Pbcao and Ybco/Pbcgo Nanometer Multilayers

“…Our transport measurements 1,2,6 show that the 20% Al-and Ga-doped PBCO, abbreviated as PBCAO and PBCGO, have electrical resistivities several orders of magnitude higher than that of PBCO at temperatures lower than 77 K. The PBCAO and PBCGO can therefore provide much better insulation for YBCO or PBCGO layers. Within our experimental uncertainty, the superconducting onset T c appeared to be the same for all PBCAO and PBCGO layers regardless of their difference in thickness.…”