Noun
non-stoichiometric compound- any chemical compound in which the number of atoms of each element is not expressible as the ratio of small integers; normally due to missing atoms in a solid state lattice
...Nonstoichiometry is pervasive for transition metal oxides, especially when the metal is not in its highest oxidation state.. pp. 642-644 For example, although wüstite (ferrous oxide) has an ideal (stoichiometric) formula FeO, the actual stoichiometry is closer to Fe0.95O. For each "missing" Fe2+ ion, the crystal contains two Fe3+ ions to balance the charge. The composition of a non-stoichiometric compound usually varies in a continuous manner over a narrow range. Thus, the formula for wüstite is written as Fe1-xO, where x is a small number (0.05 in the previous example) representing the deviation from the "ideal" formula. Nonstoichiometry is especially important in solids, which are three-dimensional polymers and which tolerate mistakes. To some extent, entropy drives all solids to be non-stoichiometric. But for practical purposes, the term describes materials where the non-stoichiometry is measurable, usually at least 1% of the ideal composition. Read full entry
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- 1.Non-stoichiometric compound - Wikipedia, the free encyclopedia
- Non-stoichiometric compound. From Wikipedia, the free encyclopedia. Jump to: ... The composition of a non-stoichiometric compound usually varies in a continuous ...
- http://en.wikipedia.org/wiki/N
on-stoichiometric_compound
- 2.PRET Homepage
- The Center for Non-Stoichiometric Semiconductors is led by UCSB with one primary ... optoelectronic properties of non-stoichiometric compound semiconductors, and to ...
- http://www.ece.ucsb.edu/pret/h
ome.html
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What is meant by the term |
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A nonstoichiometric compound is anything in which the elements do not occur in proportions of whole numbers. Usually these are solids which have some defect in their crystal lattice structure, meaning it is missing some ions. A common example is of the three biggies in the iron oxides. Fe2O3 and Fe3O4 are typically stoichiometric... if you have 2 million Fe ions in your Fe2O3, you will have very near 3 million O ions. FeO, on the other hand, is often slightly short of iron, and is written Fe(1-x)O, in which x is some small number. |
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