Structural aspects, superconductivity and thermal properties of Pr in the La1-xPrxCaBaCu3O7-δ system with 1.0 ≥ x ≥ 0.0

Abstract We report on the structural aspects and superconductivity of the La 1− x Pr x CaBaCu 3 O 7− δ system (RE: 1113) with x =0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 1.0. X-ray diffraction studies show that Pr substitutes isostructurally in LaBaCaCu 3 O 7− δ (La: 1113) until complete replacement of La. The superconducting transition temperature, T c , determined from AC susceptibility measurements decreases with x . The relative T c depression due to Pr in the LaBaCaCu 3 O 7− δ system is less in comparison to that found for La site Pr substituted LaBa 2 Cu 3 O 7 system. Normal state DC magnetism of the Pr substituted samples show a Curie–Weiss paramagnetic susceptibility with deviations below about 10 K. The non-superconducting compounds ( x =0.7, 1.0) display Schottky-type anomalies which are attributed to crystalline electric field effects (CEF). The related entropy change for x =1.0 sample amounts to Δ S =7.75 J/mol K. Rietveld analysis on neutron diffraction pattern of x =0.0 sample shows that 46 at% of the La is occupying the Ba site, in normal Re: 123 unit cell. A similar situation is suppose to occur in case of PrBaCaCu 3 O 7 , for which the refinement of Ba and Pr sites is near impossible due to their similar scattering cross-sections for neutrons. Ba site sitting Pr does not contribute to the Pr-4f hybridization with Cu–O conduction band, giving rise to a lower T N and less effect of Pr on superconductivity of La: 1113 system than for La: 123. The results strengthen extended Pr-4f hybridisation with Cu–O conduction band.