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What is non-stoichiometric defect example?

What is non-stoichiometric defect example?

Types of Non-Stoichiometric Defect: Metal excess defect due to the presence of extra cations at interstitial sites: Here, on heating the compound, it releases extra cations. These cations occupy the interstitial sites in crystals and the same number of electrons goes to neighbouring interstitial sites.

What are the types of non-stoichiometric defect?

Nonstoichiometric inorganic solids contain the constituent elements in a non-stoichiometric ratio due to defects in their crystal structures. These defects are of two types: (i) metal excess defect and (ii) metal deficiency defect.

What is stoichiometric defect and non-stoichiometric defect?

Stoichiometric defects are those that do not disturb the stoichiometry of a compound. Nonstoichiometric defects are defects in crystal structures that disturb the stoichiometry of the crystal. Effect on Stoichiometry. They do not affect the stoichiometry of the compound. They change the stoichiometry of the compound.

What are non-stoichiometric defects Class 12?

Non stoichiometric defects:- If a result of the imperfactions in the crystal the ratio, of the cations and anions becomes difference from that indicated by ideal chemical formula. The defects are called non-stoichiometric defects.

What are two types of stoichiometric defects?

-There are two types of stoichiometric defects. One is schottky defect and the other is frenkel. Schottky defect occurs when equal numbers of cations and anions are missing from the lattice. -Frenkel defect arises when an ion is missing from its actual lattice site and it occupies any interstitial site.

How many types of stoichiometric defects are there?

Stoichiometric defects are intrinsic defects in which the ratio of cations to anions remains exactly the same as represented by the molecular formula. They are mainly of two types: Vacancy defects in which an atom is not present at its lattice sites causing that lattice site to be vacant and create a vacancy defect.

What is stoichiometric defect example?

Is Schottky defect stoichiometric?

So, both Frankel and Schottky defects are stoichiometric defects. When an equal number of cations and anions are missing from the lattice then arises Schottky defects. Both cations and anions are the same because the density of crystal decreases in ionic compounds of higher coordination numbers.

What are Schottky and Frenkel defects?

In Schottky defect the difference in size between cation and anion is small. Frenkel defect contains ionic crystals where the anion is larger than the cation. Both anion and cation leave the solid crystal. Atoms permanently leave the crystal.

How does Schottky defect arise?

A Schottky defect is an excitation of the site occupations in a crystal lattice leading to point defects named after Walter H. Schottky. In ionic crystals, this defect forms when oppositely charged ions leave their lattice sites and become incorporated for instance at the surface, creating oppositely charged vacancies.

What are the conditions of Schottky defect?

Schottky defects usually occur when heat is applied to the ionic compound crystal. Heat raises the temperature, and hence the thermal vibration within the crystal. This creates gaps in the crystal pattern. The gaps are created in stoichiometric ratio, i.e. as per the availability of ions in chemical compounds.

What is Schottky defect give an example?

The compound lattice has only a small difference in sizes between the anions and cations. Some common example of salts where Schottky defect is prominent include Sodium Chloride (NaCl), Potassium Chloride (KCl), Potassium Bromide (KBr), Caesium Chloride (CsCl) and Silver Bromide (AgBr).

Which is the best description of a non stoichiometric defect?

Non-stoichiometric defect: The defect that causes the ratio of the number of cations to anions to be different from that indicated by the ideal chemical formula is known as a non-stoichiometric defect. Non-stoichiometric defects are of two types – metal excess defects and metal deficiency defects.

Are there any non stoichiometric defects in crystalline solids?

The defects discussed so far do not disturb the stoichiometry of the crystalline substance. However, a large number of non-stoichiometric inorganic solids are known which contain the constituent elements in non-stoichiometric ratio due to defects in their crystal structures. These defects are of two types:

Why do non stoichiometric compounds have special properties?

The type of equilibrium defects in non-stoichiometric compounds can vary with attendant variation in bulk properties of the material. Non-stoichiometric compounds also exhibit special electrical or chemical properties because of the defects; for example, when atoms are missing, electrons can move through…

How are cation vacancies related to stoichiometric defects?

(i) Cation Vacancies: In some cases, the positive ions may be missing from their lattice sites. The extra negative charge may be balanced by some nearby metal ion acquiring two positive charges instead of one. This type of defect is possible in metals which show variable oxidation states.