We report here on the changes in behavior, including transitions from
superconducting to semiconducting, as a function of heat treatment of
YBa2(Cu1-xNi(x))3O(y) with x = 0.05. In particular, conventional mater
ials prepared by slow cooling from approximately 1200 K (designated OP
for oxygenating preparations), show superconducting onset temperature
s of T(c) approximately 75 K. This is also the case when materials are
quenched from air annealing temperatures T(A) greater-than-or-equal-t
o 1123 K and subsequently reoxygenated at T(a) = 673 K. However, when
OP are air annealed at T(A) = 1023 K, quenched to liquid N2 (designate
d K parent or K(p) in this state), and subsequently reoxygenated at T(
a) = 673 K (designated as K(o) compound), no superconductivity is obse
rved in the resistivities down to 4.2 K. Also, magnetic susceptibiliti
es of K(o) compounds show relatively large effective magnetic moments
and either no, or only trace amounts of, superconductivity. Both K(p)
(quenched from T(A) = 1023 K) and K(o) were orthorhombic, while the co
nventional parents (quenched from T(A) greater-than-or-equal-to 1123 K
) were tetragonal. Possible origins for this unusual K(o) phenomenolog
y are discussed and comparisons are drawn with other cases where therm
al treatment results in loss of superconductivity.