Crystals have defects due to imperfections that occur during their formation or as a result of external factors such as temperature, pressure, or radiation. These defects can arise from various sources, including the misalignment of atoms, vacancies (missing atoms), interstitials (extra atoms in the lattice), or impurities from foreign elements. Such defects can significantly affect the physical properties of the material, including its strength, electrical conductivity, and optical characteristics. Ultimately, while ideal crystals have a perfect arrangement, real-world conditions often lead to these imperfections.
A common type of point defect that occurs in a crystal of zinc sulphide is a vacancy defect. In this defect, an atom is missing from its lattice position, creating a gap or a vacancy in the crystal structure.
In the frenkel defect the ions are not removed from the crystal.so there will be no change in the crystal structure. that is there is no decrease in the no of ions.all the ions are inside the crystal.they are only dislocated.
1).schottky defect arises due to departue of ions (both cation and anion in equal ratio) from crystal lattice leaving holes that favour conductivity. The equal no of ions depart because to maintain the electrical neutrality of crystal. It was discovered by walter.H schottky in 1930. But in frenkel defect ions(cations) are missing from there normal lattice site and occupying an interstitial site between the lattice points. They dont depart from crystal lattice. Because no departure occure so crystal remain electrically neutral. It was discovered by Yakov frenkel in 1926. 2) schottky defect is only vacancy defect but frenkel defect is vacancy as well as interstitial defect. 3). Schottky defect decreases density and strength of the crystal. But frenkel defect doesnt affect density. 4).schottky defect is shown by the ionic solids having high coordination no and approx. same size of cation and anion(i.e r+ve/r-ve approaches to 1) While frenkel defect is shown by the compound having low coordination no and size of anion larger than cation(i.e r+ve/r-ve approches the minimum value). By Sandeep Singh Lingwal Srinagar, Uttrakhand
When AgCl is doped with CdCl2, a Schottky defect is produced. This occurs when an equal number of cations and anions are missing from their lattice sites, leading to the formation of vacancies in the crystal structure.
Yes, a crystal with Schottky defects can have a change in volume due to the vacancies created by the missing atoms. This can lead to a decrease in the total volume of the crystal, impacting its overall density and properties.
Both Frenkel and Schotty defects improve the electrical conductivity of an ionic crystal.
When the both the cations and anions are absent from the crystal lattice it is called Schottky defect. This defect is shown when the anions and cations have comparable size. The Frenkel defect is shown by ionic molecules when their is a large difference in the size of anions and cations. The smaller anions are very much mobile and they occupy interstitial site. AgBr has cations and anions with comparable size and hence it shows Schottky defect but the Ag+ ion is very much mobile and it easily occupies interstitial place getting dislocated from its original place, that's why the ionic crystal AgBr shows both Schottky and Frenkel defects.
Within a crystal there are point defects and line defects; point defects are missing or extra lattice points within the crystal lattice (vacancies or interstitials), line defects may be due to an 'extra' half lattice plane within the crystal. The end of a line defect plane is known as an edge dislocation, screw dislocations occur where part of a crystal is displaced over one lattice direction and is therefore twisted. Dislocation loops can occur where an edge and a screw dislocation intersect.
Ionic defects are structural imperfections in a crystal lattice that result from the presence of missing or extra ions in the lattice. These defects can affect the material's properties, such as electrical conductivity or optical behavior, by influencing the movement of ions within the lattice. Examples of ionic defects include vacancies, interstitial ions, and substitutional impurities.
A defective product has a defect: "My phone is defective" "What defect does it have?" "The defect is that the screen is broken" To defect can also mean to switch sides e.g. from an army or a political party
Depends, what defect?
The defect forms when oppositely charged ions leave their lattice sites, creating vacancies. These vacancies are formed in stoichiometric units, to maintain an overall neutral charge in the ionic solid. The vacancies are then free to move about as their own entities. Normally these defects will lead to a decrease in the density of the crystal.