Synthesis and superconducting properties of (Y1−xPrx)Ba2Cu4O8 and (Y1−xPrx)2Ba4Cu7O15−y compounds

Both (Y1−xPrx)Ba2Cu4O8 (hereafter abbreviated as Y/Pr124) and (Y1−xPrx)2Ba4Cu7O15−y (Y/Pr247) compounds were successfully synthesized over the whole concentration range 0≤x≤1 by means of either hot isostatic pressing (HIP) technique or high pressure oxygen gas technique. We revealed that the superconducting transition temperature disappears at xc=0.8 in both systems in contrast to xc=0.5 for the (Y1−xPrx)Ba2Cu3O7 (Y/Pr123) system reported in the literature and concluded from this that the suppression of superconductivity due to the Pr-doping is weaker in both 124 and 247 systems than that in the 123 system. Furthermore, a combination of the magnetic susceptibility data in the normal state with the Pr–O distance derived from the neutron diffraction experiments led us to conclude that the Pr ion is in the trivalent state for all samples in both 124 and 247 systems. An increase in the critical concentration xc in the Y/Pr124 and Y/Pr247 systems relative to that for the Y/Pr123 system is attributed to an increase in the hybridization of the Pr-4f and O-2p orbitals.