Abstract
We have investigated the influence of the incorporation of Ca and Nd ions on the structural and superconducting properties of the system by Rietveld refinement of x-ray diffraction patterns of seven samples, i.e. , 0.10, 0.20, 0.30, 0.40, 0.50 and 0.60 together with a.c. susceptibility and oxygen content measurements. X-ray data confirm the occurrence of a single-phase tetragonal structure with a space group of for all the seven samples and all Nd ions exclusively occupy La sites. Ca substitutes onto the La sites with a concomitant displacement of La onto the Ba sites for and for ; most of the Ca, %, enters La sites with some fraction occupying Ba sites. Samples with are superconducting and is between 42 and 80 K. With increasing x = y, both the hole concentration in the -O layers and increase to a maximum value of 0.309 and 80 K respectively at . An approximate correlation between and the hole concentration is suggested.
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