The effect of substitution at the Cu site by the transition elements Fe, Co, Ni, and Zn on the structure and superconducting properties of ${\mathrm{NdBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ has been investigated. Compared to the ${\mathrm{YBa}}_2$${\mathrm{Cu}}_{3\mathrm{-}\mathit{x}}$${\mathit{M}}_{\mathit{x}}$${\mathrm{O}}_{7+\mathrm{\delta }}$ (M=Fe, Co, Ni, Zn) system, considerably high solid solubility and drastic ${\mathit{T}}_{\mathit{c}}$ suppression is achieved in the Nd 1:2:3 system. The maximum solid solubilities achieved for the dopants are x=1.0 for M=Fe and Co and x=0.8 for M=Ni and Zn. An orthorhombic-to-tetragonal (O→T) transition is observed at x=0.08 for M=Fe, Co similar to the case of the M-doped Y 1:2:3 system. However, a second T→O transition is observed in Nd 1:2:3 at x=0.5 for M=Co and x=0.8 for M=Fe. For the Ni- and Zn-doped phases, an O→T transition is observed at x=0.4 for M=Ni and x=0.5 for M=Zn. The doped phases are superconducting up to x=0.2 (M=Fe, Co, Ni) and x=0.08 (M=Zn). The initial rate of ${\mathit{T}}_{\mathit{c}}$ suppression (up to 3.33 at. %) is ∼14 K/at. % for M=Fe, Co, and Ni and ∼28 K/at. % for M=Zn and is much higher than that reported for the Y 1:2:3 system. The Fe- and Zn-doped phases, heated in flowing ${\mathrm{N}}_2$ gas at 800 °C followed by reoxygenation at 450 °C show higher ${\mathit{T}}_{\mathit{c}}$ and sharper superconducting transition. Hole doping by Ca substitution (y) at the Nd site in the Zn-doped (x=0.1) semimetallic-semiconducting Nd 1:2:3 phase induces metallicity and superconductivity for y≥0.1 and a ${\mathit{T}}_{\mathit{c}}$ of 32 K is obtained for y=0.2.

• Received 29 July 1993

DOI:https://doi.org/10.1103/PhysRevB.48.16727