Polycrystalline samples of (${\mathrm{Pr}}_{1\mathrm{-}\mathit{x}}$${\mathit{M}}_{\mathit{x}}$)${\mathrm{Sr}}_2$${\mathrm{Cu}}_{2.7}$${\mathrm{Mo}}_{0.3}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ (M=Ca and Sr; 0≤x≤0.3;δ∼0.1) with tetragonal perovskitelike structure were synthesized and investigated by powder x-ray-diffraction, electrical-resistivity, magnetic-susceptibility, and specific-heat measurements. Superconductivity can be achieved by partially substituting Ca or Sr for Pr in semiconducting ${\mathrm{PrSr}}_2$${\mathrm{Cu}}_{2.7}$${\mathrm{Mo}}_{0.3}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$. The ${\mathit{T}}_{\mathit{c}}$ (midpoint) is about 17 K with x=0.1 for both Ca- and Sr-doped systems. The observation of the magnetic shielding effect with powder samples confirms the bulk-nature superconductivity. In addition, the reduced effective magnetic moment ${\mathrm{\mu }}_{\mathrm{eff}}$ (${\mathrm{\mu }}_{\mathit{B}}$/Pr mol) derived from the Curie-Weiss-like magnetic susceptibility of ${\mathrm{PrSr}}_2$${\mathrm{Cu}}_{2.7}$${\mathrm{Mo}}_{0.3}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ is found to increase with Ca or Sr doping, while the linear term coefficient γ (mJ/Pr mol ${\mathrm{K}}^2$) of specific heat is almost independent of the doping. These results are discussed in conjunction with hole-filling and hybridization effects for the quenching of superconductivity in ${\mathrm{PrSr}}_2$${\mathrm{Cu}}_{2.7}$${\mathrm{Mo}}_{0.3}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ and compared with those in ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$. © 1996 The American Physical Society.

• Received 10 October 1995

DOI:https://doi.org/10.1103/PhysRevB.53.11340