Transport properties of the oxides ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Pr}}_{\mathit{x}}$${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ (0≤x≤1): Effects of band filling and lattice distortion on superconductivity

The oxides with composition ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Pr}}_{\mathit{x}}$ ${\mathrm{Ba}}_2$(${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$)(0≤x≤1) 7-δ (0≤x≤1) are characterized by x-ray diffraction, resistivity (ρ) and thermoelectric power (S) measurements. X-ray diffraction shows an orthorhombically distorted perovskite structure for all compositions, the pseudotetragonality increasing with x. The substitution of the tetravalent Pr for the trivalent Y atom increases the band filling in these materials. As a consequence, the superconducting transition temperature is progressively decreased with increasing x, and S significantly increases. Thermopower and resistivity measurements indicate that these oxides have relatively narrow bands and that the electronic correlations dominate their properties.