Role of Pr in Eu-123 high Tc nanometer-sized superconductors

Samples of Eu_1−xPr_xBa₂Cu₃O_7−δ with compositions x=0.0, 0.1 and 0.3 were prepared by the solid state reaction route. The structural, electrical and microstructural properties were investigated by X-ray diffraction, Physical Property Measurement System (PPMS) and scanning electron microscopy (SEM) techniques respectively. The lattice parameters, oxygen deficiency, hole concentration in the CuO₂ plane, average charge on Cu–O plane were evaluated from X-ray diffraction data. From XRD data, it is observed that the lattice parameters and oxygen deficiency increase with increasing Pr concentration. It was also observed that the hole concentration in CuO₂ plane and average charge on Cu–O plane decrease with increasing Pr concentration. The electrical resistivity of all samples was measured in the temperature range 300 K to 4 K. It was found that the normalized transition temperature decreases with increasing Pr concentration. This may be due to reduction in hole concentration or average charge on Cu–O plane. From scanning electron microscopy images, it was observed that grain size increases with increasing Pr concentration. This increase may be the possible cause for suppression of T_c.