Polycrystalline samples of ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Pr}}_{\mathit{x}}$${\mathrm{Sr}}_2$${\mathrm{Cu}}_{2.7}$${\mathrm{Mo}}_{0.3}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ (0≤x≤1) with tetragonal perovskite-like structure were synthesized and investigated by powder x-ray-diffraction, electrical-resistivity, magnetic-susceptibility, and specific-heat measurements. It is found that the ${\mathit{T}}_{\mathit{c}}$ decreases monotonically with Pr concentration x from ${\mathit{T}}_{\mathit{c}}$∼33 K for x=0 to ${\mathit{T}}_{\mathit{c}}$∼12 K for x=0.7. The critical concentration ${\mathit{x}}_{\mathrm{cr}}$ required to suppress the ${\mathit{T}}_{\mathit{c}}$ to zero is estimated to be around 0.85. Even though the ${\mathrm{PrSr}}_2$${\mathrm{Cu}}_{2.7}$${\mathrm{Mo}}_{0.3}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ exhibits a semiconducting behavior, the normal-state resistivity at T≥100 K remains nearly the same order of magnitude as that of superconducting ${\mathrm{YSr}}_2$${\mathrm{Cu}}_{2.7}$${\mathrm{Mo}}_{0.3}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$. An effective magnetic moment ${\mathrm{\mu }}_{\mathrm{eff}}$∼3${\mathrm{\mu }}_{\mathit{B}}$ is obtained from the simple Curie-Weiss law and a huge linear term coefficient of specific heat γ∼440 mJ/mol ${\mathrm{K}}^2$ is determined for ${\mathrm{PrSr}}_2$${\mathrm{Cu}}_{2.7}$${\mathrm{Mo}}_{0.3}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$.

No magnetic transition is observed for ${\mathrm{PrSr}}_2$${\mathrm{Cu}}_{2.7}$${\mathrm{Mo}}_{0.3}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ down to 0.6 K. However, a superconducting transition with ${\mathit{T}}_{\mathit{c}}$∼17 K is seen by partially substituting Ca for Pr in ${\mathrm{Pr}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Ca}}_{\mathit{x}}$${\mathrm{Sr}}_2$${\mathrm{Cu}}_{2.7}$${\mathrm{Mo}}_{0.3}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$. The similarities and differences in superconductivity and magnetism between ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Pr}}_{\mathit{x}}$${\mathrm{Sr}}_2$${\mathrm{Cu}}_{2.7}$${\mathrm{Mo}}_{0.3}$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ and ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Pr}}_{\mathit{x}}$${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ are compared and discussed.

• Received 20 September 1994

DOI:https://doi.org/10.1103/PhysRevB.51.8543