Tl valence change andTcenhancement(>130 K)in(Cu,Tl)Ba2Ca2Cu3Oydue to nitrogen annealing

Annealing effects in a reducing environment (flowing nitrogen) in the temperature range of $200--600\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ are reported on the high Tl content $({\mathrm{Cu}}_{1\ensuremath{-}x}{\mathrm{Tl}}_{x}){\mathrm{Ba}}_{2}{\mathrm{Ca}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$ system, synthesized under high pressure (4.5 GPa). A considerable enhancement in ${T}_{c}$ from 97 K (as-synthesized) to $g130 \mathrm{K}$ (annealed at $550\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ and an anomalous behavior in the resistivity with annealing is found. The results have been analyzed in the context of the loss of oxygen and Tl valence change.