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When the crystallisation process happens at a very quick rate, point flaws are accounted for in the calculation. The majority of these flaws are caused by a divergence in the arrangement of the constituent particles. When the ideal arrangement of solids in a crystalline solid is deformed around a point or atom, this is referred to as a point defect.
Classification
Defects or imperfections in crystalline solids can be classified into four types: line defects, point defects, volume defects, and surface defects. Line defects are the most common type of defect in crystalline solids. Crystal point defects were initially observed in ionic crystals, rather than in metal crystals, which were much simpler at the time of discovery.
Classification of point fault
Defect in the stoichiometric equation
Defective Frenkel
Schottky’s flaw is a type of defect.
In this type of point defect, the ratio of positive and negative ions (Stoichiometric) and electrical neutrality of a solid are not altered, although in the other types of point defects, they are. It is also referred to as intrinsic or thermodynamic flaws in some cases.
Fundamentally, they can be divided into two categories:
Vacancy defect:
When an atom is not present at one of their lattice sites, that lattice site is considered unoccupied, and a vacancy defect is created as a result. The density of a substance reduces as a result of this phenomenon.
In crystals, an interstitial defect is a defect in which an atom or molecule occupies the intermolecular spaces between neighbouring molecules. The density of the substance increases as a result of this flaw.
A non-ionic compound is characterised mostly by vacancy and interstitial flaws. When it comes to the Frenkel and Schottky defects, an ionic molecule exhibits the same behaviour.
1. In ionic solids, the smaller ion (cation) generally moves out of its place and occupies an intermolecular space, which is known as the Frenkel defect. Vacancy defects are formed on the original position, while interstitial defects are experienced on the new position in this scenario.
It is referred to as a dislocation defect in some circles.
The density of a substance does not change over time.
It occurs when there is a significant discrepancy in the size of anions and cations in a solution.
For instance, ZnS and AgCl are both metals.
The type of Schottky Defect
It is possible to find this type of vacancy defect in ionic solids. However, with ionic compounds, we must maintain the electrical neutrality of the compound in such a way that an equal number of anions and cations are absent from the compound, which is difficult.
It has the effect of decreasing the density of the material.
In this case, the sizes of the cations and anions are nearly the same size.
Impurity Defect:
To better comprehend the impurity defect, consider the following example. The Sr2+ ions in molten NaCl replace two Na+ ions and take up the space of one Na+ ion when the compound SrCl2 is used to crystallise the solution. As a result, the lattice site of one Na+ becomes unoccupied, resulting in the formation of an impurity defect.
Non-Stoichiometric Defect:
In this defect, the cation-to-anion ratio is altered, either by the addition or removal of ions, depending on the situation.
Non-Stoichiometric Defects are classified into the following categories:
Defect due to a lack of metal: In this case, the solids have a smaller number of metals in comparison to the Stoichiometric proportion indicated above.
A metal surplus defect can be classified into two types: (1) metal overproduction and (2) metal overproduction and overproduction.
Anionic vacancies cause an overabundance of metal defects in the following ways: As a result of the absence of anions from their initial lattice location in crystals, this phenomenon happens. As a result, electrons take up residence in the space previously occupied by anions.
Due to the existence of additional cations at interstitial locations, there is an excess of metal in the defect: In this case, heating the chemical causes it to release additional cations. These cations occupy the interstitial sites in crystals, and the same amount of electrons is transferred to the interstitial sites in the vicinity of the cations.
Crystalline solids, their structure, and their flaws are all fascinating subjects to investigate. This is only a brief introduction to point defects in solids.
Classification of Stoichiometric defects
Vacancy defect: If the atoms at their lattice sites are no longer present, then there is a vacant lattice site, which results in the formation of the “vacancy defect.” The density of the substance decreases as a result of this. Defect in the interstitial space: An interstitial defect is a type of defect in which a molecule or an atom occupies intermolecular gaps in a crystal, causing the crystal to crack. The density of the material increases as a result of this sickness. Non-ionic compounds exhibit interstitial and emptiness defects in particular, while ionic compounds exhibit the same defects in Schottky and Frenkel defects.
Conclusion
Therefore it can be concluded ,non-ionic chemical is characterised by the presence of interstitial and vacancy flaws in its structure. An ionic compound is used to illustrate the Schottky and Frenkel defects in semiconductors. Defect of Frenkel in most ionic solids, the smaller ion (known as the cation) displaces the larger ion (known as the anion) and takes up residence in intermolecular space.
