Control on the Copper Valence and Properties by Oxygen Content Adjustment in the LaCuO3−ySystem (0≤y≤0.5) |
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| Authors: | M Karppinen H Yamauchi H Suematsu K Isawa M Nagano R Itti O Fukunaga |
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| Institution: | aMaterials and Structures Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama, 226, Japan;bLaboratory of Inorganic and Analytical Chemistry, Helsinki University of Technology, FIN-02150, Espoo, Finland;cResearch and Development Center, Tohoku Electric Power Co., Inc. Sendai, 981, Japan;dSuranaree University of Technology, Nokhon Ratchasima, 30000, Thailand;eDepartment of Inorganic Materials, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, 152, Japan |
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| Abstract: | The LaCuO3−yperovskite is considered as the first member of the 01(n−1)nseries of “layered cuprates.” Highly oxidized, stoichiometric LaCuO3is stabilized under very high oxygen pressures, and was synthesized in a cubic-anvil-type high-pressure apparatus at 5 GPa and 1400°C using excess amounts of KClO4as an external oxidizing agent. Upon heating under ambient pressure the rhombohedral high-pressure phase loses oxygen yielding tetragonal, monoclinic, and orthorhombic forms of LaCuO3−yas intermediate products before the final decomposition into La2CuO4and CuO or Cu2O around 800°C. All three oxygen-deficient LaCuO3−yphases could be isolated and their stability limits and corresponding oxygen contents conveniently investigated by annealing stoichiometric LaCuO3in a thermobalance of high sensitivity in order toin situdetect the exact amount of oxygen loss. The nominal copper valence values calculated from the oxygen contents are compared and discussed with XPS data as well as with the results evaluated from magnetic susceptibility measurements. |
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