Schottky defect occurs in those ionic crystals where the difference in size between cation and anion is small . Frenkel defect usually occurs in those ionic crystals where size of anion is quite large as compared to that of the cation. In Schottky defect, both cation and anion leave the solid crystal.
What is Schottky defect class 12?
-A Schottky defect is a type of vacancy defect which is found in ionic solids . It is a stoichiometry defect (thermodynamic defect), which means that such defects do not change or distort the stoichiometry of the solid.
What is Schottky defect?
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 is Schottky defect and Frenkel defect 12?
| Schottky defect Frenkel defect | It occurs when the atoms are totally missing from the crystal lattice. It occurs when the atoms are just displaced from their position to some voids or interstitial sites of the crystal lattice. |
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What is the difference between a Schottky defect and Frenkel defect?
In Schottky defect, both cation and anion leave the solid crystal. In Frenkel defect, only the smaller ion (cation) leaves its original lattice site; whereas, the anion remains in original lattice sites. The atoms permanently leave the crystal. ... One Frenkel defect creates one vacancy and one self-interstitial defect .
How are Schottky defects calculated?
The number of Schottky defects (n) present in an ionic compound containing N ions at temperature T is given by n = Ne^ (-E//2KT), where E is the energy required to create n Schottky defects and K is the Boltzmann constant, If the mole fraction of Schottky defect in NaCl crystal at 2900 K is X, then calculate -ln(x), <br ...
What are consequences of Schottky defect?
Consequences of Schottky defect:
Hence, the density of a substance decreases. ii. The number of missing cations and anions is equal . Hence, the electrical neutrality of the compound is preserved.
Which one of the Schottky defects are?
Definition. Schottky defect is a type of point defect or imperfection in solids which is caused by a vacant position that is generated in a crystal lattice due to the atoms or ions moving out from the interior to the surface of the crystal.
What is Schottky defect Toppr?
Schottky defect is a type of point defect . It is a stoichiometric defect in which both cations and anions remain missing from their lattice site in equal numbers and hence stoichiometry and electrical neutrality is maintained.
What is sprinkled effect?
In Frenkel defect, an ion is displaced from its lattice place to an interstitial place. So, there is no loss or gain of ions in lattice structure. It involves only the migration of the ions within the crystal, thus preserving both volume and mass. Therefore, there is no any change in density of the of the crystal.
What is Frenkel defect explain it?
A Frenkel defect is a type of point defect in crystalline solids , named after its discoverer Yakov Frenkel. The defect forms when an atom or smaller ion (usually cation) leaves its place in the lattice, creating a vacancy and becomes an interstitial by lodging in a nearby location.
> Since in NaCl, KCl the size of anions and cations are similar, they do not show Frenkel defects. > In CsCl and AgCl, there is a large difference in the size of anions and cations , but CsCl being an alkali halide does not show Frenkel defect.
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.
Can Schottky defects exist in K2O?
(1) Yes , Schottky defects can exist in K2O; each defect will consist of one O2- vacancy and two K+ vacancies.
Why are Schottky defects found in NaCl?
The animation shows a Schottky defect in NaCl. Schottky defects are point defects that occur when a pair of ions leave the structure. Consequently there is a relaxtion of the ions around the vacant site and slight increase in volume . ...
How many ions are needed for one Schottky defect?
M 2 X 3 : one Schottky defect equals two cation and three anion vacancy .
