Frenkel Defect
The Frenkel defect occurs when an ion disappears from its normal state and occupies an interstitial site between lattice points. The existence of a hole due to a missing cation from its normal position and occupying the interstitial position is shown. In this case, also, the crystal remains electrically neutral because the number of anions and cations remains the same This defect is also known as an interstitial defect. It creates vacancy defects. It has its original position and an interstitial defect in its new location.
The Frenkel Defect in a crystal is shown in the image added below.
Conditions for Frenkel Defects
This defect generally occurs in compounds in which the coordination number is low, anions are much larger than the cations.
In perfect alkali metal halides, these defects are not very common because the ions cannot move to the interstitial state due to their large size. Defects can be found in silver halides such as AgCl, AgBr, AgI, ZnS, etc. So far as of the small size of the Ag ions and ions, these ions can move into the interstitial sites.
Vacancies or holes exist in crystals that have a Schottky well as well as a Frenkel defect, but the former decreases the overall density of the substance, but the latter does not. , another hybrid type of defect can also arise from a combination of both.
Effects of Schottky and Frenkel Defects
Defects in Schottky and Frank crystals give some interesting results. These are-
- The presence of these defects increases the electrical conductivity of crystals. When an electric field is about the experiment, an adjoining ion moves from its lattice site to occupy a hole. As a result, a new hole is created and another nearby ion moves into it, and so on. This process continues and thus he moves from one end to the other. Thus, it conducts electricity throughout the crystal.
- Due to the impendence of pores in the crystal, its density changes. It presumably noted that the density decreases only for crystals with Schottky defects. However, there is no change in denisty in case of Frenkel defect
- The presence of pores also reduces the lattice energy or stabilization of the crystal. The presence of too many pores can cause partial collapse of the lattice.
- In Frenkel defects, the dielectric constant of the crystal is increased by placing it in a pattern of equal charges.
Point Defects
Solids are made up of a lot of small crystals. However, the defect in solids occurs during the crystallization process due to the fast or moderate rate of crystal formation. Defects are described as irregularities in the arrangement of constituent particles in general. The defect could be a point or a line defect based on the irregular arrangement. A deviation point defect occurs in an ideal crystal when there are anomalies in the arrangement around any point or atom in the crystal. Similarly, a line defect occurs when there is a variation in the arrangement of the entire row of lattice points in crystals.
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