Abstract
The cation stoichiometry and the tunability of oxygen content in the Ba 1–y CuO 2+δ phase were investigated by means of various methods of chemical analysis. Samples with different nominal metal stoichiometries, y nom ranging from 0 to 0.1, were synthesized. Single-phase samples were obtained for y nom ≈0.1, i.e. with about 10 mol% barium deficiency. The possibility to stabilize the Ba 1–y CuO 2+δ phase with different oxygen stoichiometries was studied thermogravimetrically. Under an argon atmosphere below 400 °C a part of the excess oxygen of the fully oxygenated Ba 0.9 CuO 2.01 sample was found to be released in two steps leading to stoichiometries of Ba 0.9 CuO 1.97 and Ba 0.9 CuO 1.94 . On the other hand, above 400 °C it was possible to continuously tune the oxygen stoichiometry at least down to Ba 0.9 CuO 1.85 (700 °C). A decrease in the copper valence with decreasing oxygen content led to an increase in the effective magnetic moment obtained from the magnetic susceptibility measurements performed for two Ba 0.9 CuO 2+δ samples with different oxygen stoichiometries.
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