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DOI: 10.1039/A806773B (Paper) Reference Section for: J. Mater. Chem., 1999, 9, 465-469

Stoichiometry and copper valence in the Ba1–yCuO2+δ system

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Kaisa Peitola, Kyoichi Fujinami, Maarit Karppinen, Hisao Yamauchi and Lauri Niinistö

Abstract

The cation stoichiometry and the tunability of oxygen content in the Ba1–yCuO2+δ phase were investigated by means of various methods of chemical analysis. Samples with different nominal metal stoichiometries, ynom ranging from 0 to 0.1, were synthesized. Single-phase samples were obtained for ynom≈0.1, i.e. with about 10 mol% barium deficiency. The possibility to stabilize the Ba1–yCuO2+δ phase with different oxygen stoichiometries was studied thermogravimetrically. Under an argon atmosphere below 400[thin space (1/6-em)]°C a part of the excess oxygen of the fully oxygenated Ba0.9CuO2.01 sample was found to be released in two steps leading to stoichiometries of Ba0.9CuO1.97 and Ba0.9CuO1.94. On the other hand, above 400[thin space (1/6-em)]°C it was possible to continuously tune the oxygen stoichiometry at least down to Ba0.9CuO1.85 (700[thin space (1/6-em)]°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 Ba0.9CuO2+δ samples with different oxygen stoichiometries.

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