  This study provides an account of the bulk preparation of
TlBa2Ca2Cu3O9-{\delta} (Tl-1223) superconductor at ambient pressure, and the Tc
features under thermal-annealing conditions. The as-prepared Tl-1223 (Tc =106
K) presents a significantly higher Tc = 125 K after annealing the
polycrystalline material in either flowing Ar+4% H2, or N2 gases. In order to
understand the fundamental reasons for a particular Tc, we refined the average
bulk structures using powder X-ray diffraction data. Although Ar+4%H2 annealed
Tl-1223 shows an increased c lattice parameter, it is approximately unchanged
upon N2-anneal. Due to such indeterminate conclusions on the average structural
changes, local structures were investigated at using aberration-corrected
scanning-transmission electron microscopy technique. Similar compositional
changes in the atomic arrangements of both annealed-samples of Tl-1223 were
detected in which the plane containing Ca atomic layer gives a non-uniform
contrast, due to substitution of some heavier Tl. In this report, extensive
bulk properties are summarized through temperature-dependent resistivity, and
shielding and Meissner fractions of magnetic susceptibility results; the bulk
and local structures are investigated to correlate to properties.
