In most oxides, the oxygen content is never perfect, especially in powder and ceramics. The oxygen deficiency can change the crystal structural, microstructures and properties. In a refinement, the occupancy of oxygen is assumed to be perfectly 100%. How we can explain/show the chemistry of the materials? What is the influence of oxygen content on the structure and properties?
Oxygen deficiency presents commonly as oxygen vacancy in oxides. It can cause oxygen ion conduction or electronic conduction (as charge compensation), sometimes both. Oxygen vacancy usually produces lattice expansion. It also has effect on magnetic and optical properties because it changes the electronic band gap. Rietveld refinement on Neutron diffraction pattern and EPMA examination may be help with the determination of exact oxygen value. Also, XPS can be used to determine the valence state of metal elements, by which the oxygen value can be calculated indirectly.
Dear Vijay, I fully agree with Prof. H. Zhao regarding the impact of oxygen stoichiometry on the physicochemical properties of oxide materials.You can also use iodometric titration to determine the oxygen content of the oxide. See this publication in the researchgate (https://www.researchgate.net/publication/222878917_Oxygen_content_determination_in_perovskite-type_cobaltates).
Best regards,
Chung-Yul
Article Oxygen content determination in perovskite-type cobaltates
It should be emphasized specially that most of common oxides have negligeable deviations from the stoichiometry, so for conventional engineering practice sometimes it is possible to "forget" about it. However, for oxide or oxygen containing so-called "interstitial phases", e.g. titanium monooxide TiOx, this factor is extremely important.
To Prof. H. Zhao: "...Oxygen vacancy usually (?! - my sign) produces lattice expansion..." Are you sure? Can you prove it for non-stoichiometric oxides?!
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