Substitution of M=Zn or Ni impurities in 1:2:3 (${\mathrm{Ca}}_{0.4}$${\mathrm{La}}_{0.6}$)(${\mathrm{Ba}}_{1.35}$${\mathrm{La}}_{0.65}$)(${\mathrm{Cu}}_{1\mathrm{-}\mathit{z}}$${\mathit{M}}_{\mathit{z}}$${)}_3$${\mathrm{O}}_{\mathit{y}}$ depresses ${\mathit{T}}_{\mathit{c}}^{\max }$ with almost equal effectiveness, i.e., -9 and -7 K/%, respectively. (In YBCO, Zn is three times more effective in depressing ${\mathit{T}}_{\mathit{c}}$ than Ni.) In these impurity-containing materials, the dependence of thermopower on ${\mathit{T}}_{\mathit{c}}$/${\mathit{T}}_{\mathit{c}}^{\max }$ departs substantially from the universal behavior observed in other cuprates. There is no definite trend in the resistivity of these ceramic materials with impurity concentration z. Our results suggest pair breaking or weakening of the interaction at constant carrier density when z is increased. © 1996 The American Physical Society.

• Received 24 June 1996

DOI:https://doi.org/10.1103/PhysRevB.54.13348