Types of Point Defects

The varieties of point flaws and their effects on solids are discussed in detail in point defects. Many tiny crystals are joined together to create crystalline solids. There are a variety of crystal flaws that can be detected following crystallisation.

When crystallisation happens at a rapid pace, point flaws are accounted for. The major cause of these flaws is a misalignment of the constituent particles. Crystalline solids that have a point defect are those in which the ideal arrangement of the solids has deviated around a single point/atom.

Line flaws, point defects, volume defects, and surface defects are the four types of crystalline solid defects. Ionic crystals, rather than metal crystals, were once considered to have crystal point flaws.

Deficiencies in the crystal

The following factors cause crystal defects:

• Voids in the latticework

• Rearrangement of a lattice particle

• Four ions in non-stoichiometric ratios.

• Contaminants in the latticework

Types of point defects fall into three categories:

• An error in stoichiometry

• Frenkel defect

• Schottky defect

Stoichiometric defect: point defects types 

The stoichiometric and electrical neutrality of a solid is not affected by this kind of point defect. Internal or thermodynamic flaws are other names for this problem.

They can be divided into two categories:

Vacancy defect: When an atom is absent from a lattice site, that lattice site is unoccupied, and the vacancy defect is created. The density of a material lowers as a result of this.

The intermolecular gaps in crystals are occupied by an atom or molecule in an interstitial defect. Because of this flaw, the substance’s density is elevated.

Interstitial and vacancy flaws predominate in nonionic compounds. The Frenkel and Schottky defects of an ionic substance are identical.

Frenkel’s defect

Intermolecular space is occupied by the smaller ion, the cation, in ionic solids. Vacancy defects are formed in their original location, while interstitial defects are experienced at their new location.

A substance’s density does not vary over time. It occurs when the anions and cations vary much in size. ZnS and AgCl are two examples.

Schottky defect

It is common for ionic solids to have vacancy defects of this kind. However, with ionic compounds, we must ensure that an equal amount of anions and cations are absent from the complex in order to maintain electrical neutrality. The material becomes less dense as a result. Cations and anions are almost identical in size in this case.

Interstitial Defect 

The layers can be stopped from sliding past each other even when just a small quantity of an interstitial impurity is present.

For example, since iron forms the polar covalent bonds with carbon, the strongest steel only needs roughly 1 percent carbon by mass to be significantly strengthened.

Applying a defect in the deformation of a material

Flexon is the name given to a nickel-titanium alloy that is both flexible and fatigue-resistant. Metalworkers who made titanium-based alloy for missile heat shields found it first, and it has since become a widely used material. As a corrosion-resistant and long-lasting frame for glasses, flexon may now be utilised for a variety of purposes.

Substitutional Defect Theory in Practice

As long as the host’s contaminant structure is identical, the substitutional impurities can be seen in the molecular crystals. The crystal characteristics are mostly influenced by them. For instance, in its purest form, anthracene is a conductor of electricity. Anthracene crystals with low quantities of tetracene, on the other hand, allow for a longer electron transfer across a molecule.

Suggestions for Applying the Substitutional Defect 

If the substitutional impurities have a similar structure to the host’s impurity structure, they can be recognised in molecular crystals. They have the most effect on the crystal’s properties. Pure anthracene, for example, is an excellent electrical current conductor.

Conclusion: types of point defects

The “point defects” is used to denote both solid errors and other types of point defects. Many little crystals are joined together to produce bigger crystalline solids. The resultant crystals may have a variety of defects after crystallisation. Point defects are at fault when crystallisation happens at a faster rate. A mismatch of the component particles is the major cause of these defects. When one atom/point in a crystalline solid disturbs the flawless arrangement of solids, it is called a point defect.

The four sorts of defects that can be discovered in a crystalline solid are line faults, point defects, volume defects, and surface flaws. The crystal point defect type was initially recognised in ionic rather than metal crystals, which are considerably simpler.