Abstract:
We report an investigation of structure by x-ray diffraction, microstructure
by atomic force microscopy (AFM) and broadening of resistive transitions
in high dc magnetic fields (0–20 kOe) in Er1−yCayBa2Cu3−x(Fe, Zn)xO7−δ
(y = 0.1, 0.2; and 0 x 0.20) ceramic superconductors. The XRD
shows that the presence of Ca does not alter the known effect of Fe/Zn
substitution on the structure of the pure (y = 0) system. Substitution of both
Fe and Zn leads to a decrease in the grain size and micro-hardness.
Interesting results were obtained on the influence of various dopants on the
broadening of resistive transitions in dc magnetic fields, in general: (1) an
increase in Ca content suppresses it; (2) Zn substitution has no effect; and
(3) Fe substitution enhances it. We show that these results can be interpreted
in terms of a thermally activated flux motion (TAFM), and the effect of
various dopants on the properties like pinning barrier and anisotropy.
