What is non stoichiometric and what is non stoichiometric compound

Non-stoichiometric means that the proportion is not an integer. The components of the compound are not small integer ratios between atoms, and the composition can be changed within a certain range, which does not conform to the law of definite composition.

Non-stoichiometric compounds are also known as non-metered or non-integer compounds. The components of some compounds are not small integer ratios between atoms, and the composition can be changed within a certain range, which does not conform to the law of definite composition. In the metal system, there is a Bertolet body of variable composition (in honor of Berthollet).

In other solid compounds, the phenomenon of variable composition is also quite common. Many transition metal oxides, sulfides, nitrides, carbides, and hydrides are non-stoichiometric compounds, such as Tan1-X (and UO2+X, etc.). It is caused by crystal defects or the formation of interstitial compounds, interlayer compounds, etc., and is closely related to the properties of the material.

Hello. A "non-stoichiometric compound" is one in which the chemical composition of the compound does not correspond to the proportion occupied by different atoms in the crystal structure.

The atomic (or ionic) composition of each element can fluctuate within a certain range of proportions. Their composition does not conform to valency rules, does not obey the law of composition, and cannot be expressed as small integers, but can only be described in decimals.

Non-stoichiometric compounds can be specified in the following two ways:

1. Non-stoichiometric compounds specified in the pure chemical definition refer to homogeneous phases that can be determined by chemical analysis, X-ray diffraction analysis and equilibrium vapor pressure determination and whose composition deviates from the stoichioimetry, such as FeO1+Y.

2. From the point of view of lattice structure, the deviation of the composition of non-stoichiometric compounds may also be so small that they cannot be detected by chemical analysis or X-ray diffraction analysis, etc., but they can be studied by measuring their optical, electrical, and magnetic properties. This kind of compounds with low deviation from stoichiometry have important technical properties, and are the focus of discussion in solid chemistry and therefore inorganic materials chemistry.

Here are some examples:

Olivine-type lithium iron phosphate can be used as a cathode material for lithium-ion batteries, and its structural formula is LiFePO4, in which lithium can even completely protrude from the crystal lattice to form layered FePO4, and lithium iron phosphate is a non-stoichiometric compound in most cases.

Stoichiometric formula of compounds: MO

Molecular formula of oxides with cationic vacancies: m1-xo causes the formation of non-stoichiometric compounds: caused by temperature and atmosphere.

The ratio of the atomic number of a compound does not conform to the law of proportionality, that is, it is not a simple fixed proportional relationship.

See Article 35.

Also known as non-proportional compounds, it is explained more clearly here.

To put it simply, there is no fixed proportion of the compound, and I don't know exactly how to define it.

Here are some examples:

Olivine-type lithium iron phosphate can be used in the cathode material of lithium-ion batteries, and the structural formula of its peel is LiFePO4, in which the lithium can even completely protrude from the crystal lattice to form a layered FePO4, and the lithium iron phosphate Qiaozheng ridge is a non-stoichiometric compound in most cases.

Stoichiometric Formula of Compounds:

MO oxide with cationic vacancy molecular formula: M1-XO Causes of the formation of non-stoichiometric compounds: caused by temperature and atmosphere.