Abstract
We report here on the preparation, X-ray diffraction with Rietveld refinement,
AC magnetic susceptibility measurements and effect of heat treatments in
(Y1−xNdx )SrBaCu3O6+z. Each sample was subject to two types of heat treatment:
oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. For
each x, the [AO] heat treatment increases the orthorhombicity ! = (b − a)/(b + a)
(for 0 "x <1), Tc (for x >0.2) and the distance d[Cu(1)(Sr/Ba)] (decrease Tc) for
x < 0.25 and decrease it (increase Tc) for x > 0.25. When x increase from 0 to 1,
! decreases to 0 with transition from orthorhombic to tetragonal structure. ![O] decreases
with Tc[O]. However, Tc[AO] decreases with ![AO] until x = 0.2, increases
for x = 0.4 and after it decreases by 9.8 K to 77.2 K for x = 1 [AO]. Remarkable
correlations were observed between Tc(x) and the volume of the unit cell V (x); and
between "Tc(x) = Tc[AO]−Tc[O] and "!(x). A combination of several factors such
as decrease in d[Cu(1)(Sr/Ba)]; increase in cationic and chain oxygen ordering; the
number psh(x) of holes by Cu(2)O2 superconducting plans and in-phase purity for
the [AO] samples may account for the observed data.
