To obtain a broad range of Tc for HgBa2CuO4+δ (Hg1201) by annealing, the oxidation thermodynamics and oxygen diffusion have been studied. During annealing, δ is controlled by the oxygen partial pressure P(O2) as well as the annealing temperature Ta with the oxidation enthalpy ΔH and the oxidation entropy ΔS as key parameters. Our data suggest that the ΔH of Hg1201 significantly depends on δ, which makes the ∂δ/ ∂P(O2) of Hg1201 smaller than that of YBa2Cu3O7-δ in a practical Ta range. Therefore, a wider P(O2) range are necessary. By choosing proper annealing parameters, Hg1201 samples with 0 K ≤ Tc ≤ 97 K on the underdoped side and 97 K ≥ Tc ≥ 20 K on the overdoped side were obtained.
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