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We have fabricated metal doped PrBa 2 Cu 3 O 7 (PBCO), i.e. PrBa 2( Cu 1-x M x)3 O 7 (PBCMO) with M = Al , Fe, and Ni, and x = 0.05, 0.10, 0.15, and 0.20. X-ray data indicate no significant second phase for Ni-doped samples until 15% doping level is reached. No second phase was found in Al- and Fe-doped samples up to the 20% doping level. All the doped samples are in orthorhombic structure and their lattice parameters are very close to those of YBa 2 Cu 3 O 7-δ (YBCO). However, for Al or Fe doped samples the difference in lattice parameters a-b has decreased from that of PBCO. At 77 K the electrical resistivity for Al- or Fe-doped samples is several orders in magnitude higher than that of PBCO. Therefore these compounds may be better buffer-layer materials for YBCO superconducting electronic circuits and devices.

Recently the remarkable discovery of field-induced phase transition from antiferroelectric (AFE) to Ferroelectric (FE) in ferroelectrics excited the scientific community in this field. This finding has both scientific and technological implications to us. In this paper, we studied the changes of the crystal structure when an electrical field is applied to it. The X-ray diffraction pattern reflecting these changes was discussed by theoretical calculation.

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.

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