Basicity and Solubility of Water in Solid Complex Oxides

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The Solubility of water in various solid complex oxides has been examined and discussed based on the partial acid/base reactions on the local acid and base sites in the oxides. The water dissolution reaction is defined as a overall reaction of the partial acid/base reactions below:【numerical formura】Oxygen vacancies and normal oxide ions on the normal site in the vicinity of defects or dopant cations with the highest intensity among similar sites are defined as acid site and basic site, which are favorable sites for the reactions (1) and (2), respectively. The intensity of basicity or acidity of respective sites are defined using the electronic band structure of host oxides; acid site and base site correspond to LUMO and HOMO levels of host oxides and form acceptor and proton induced levels as results of the partial reactions (1) and (2). In order to examine the concept above, both the solubility measurements on single crystals of CeO_2 doped with various kind of trivalent lanthanide ions using Secondary Ion Mass Spectrometiy (SIMS) and Photo Electron Spectroscopy and Soft X-ray Absorption/Emission Spectroscopy measurements, to compare the relatively low solubility of water in doped ZrO_2. Also examined were both the water solubility and electron spectroscopy measurements on titanates, zirconates, and cerateswith perovskitestructuredopedwithacceptordopantstoB-site. Fromtheseexperimental results, the validity of proposed partial acid/base reaction model was confirmed.