What are point defects and line defects?
In a crystalline solid, when the ideal arrangement of solids is distorted around a point/ atom it is called a point defect. Defects or Imperfections in crystalline solid can be divided into four groups namely line defects, point defects, volume defects and surface defects.
What are the different types of line defects?
- Point defects (vacancies, interstitial defects, substitution defects)
- Line defect (screw dislocation, edge dislocation)
- surface defects (material surface, grain boundaries)
- Substitutional – one atom is replaced by as different type of atom.
- Interstitial – extra atom is inserted into the lattice structure at a.
What is a planar defect?
Planar Defects. A Planar Defect is a discontinuity of the perfect crystal structure across a plane. Grain Boundaries. A Grain Boundary is a general planar defect that separates regions of different crystalline orientation (i.e. grains) within a polycrystalline solid.
Which of these are point defects?
Point defects are lattice defects of zero dimensionality, i.e., they do not possess lattice structure in any dimension. Typical point defects are impurity atoms in a pure metal, vacancies and self-interstitials.
What are the types of defects?
Quality control professionals typically classify quality defects into three main categories: minor, major and critical. The nature and severity of a defect determines in which of the three categories it belongs.
What is difference between Schottky 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.
What is Frenkel defect explain it?
The Frenkel defect (also known as the Frenkel pair/disorder) is a defect in the lattice crystal where an atom or ion occupies a normally vacant site other than its own. As a result the atom or ion leaves its own lattice site vacant.
Why does AgBr show both defects?
Schottky defect in AgBr is exhibited due to precipitation of both cations and anions. In AgBr, Ag+ ion is small in size and when removed from lattice point they can occupy interstitial sites and hence show both Frenkel and Schottky defects.
Which defect is shown by AgBr?
Solution : AgBr shows both Schottky as well as Frenkel defect. In AgBr, both Ag+ and Br- ions are absent from the lattice causing Schottky defect. However Ag+ ions are mobile so they have a tendency to move aside the lattice and trapped in interstitial site hence, cause F frendkel defect.
Which statement is true for Frenkel defect?
The density of crystals having frenkel defect is unaltered as the defect involves displacement of an atom or ion from its lattice position to an Interstitial position. So the mass and value remain unaffected.
Which of the following has Frenkel defects?
Some examples of solids which exhibit Frenkel defects:
- zinc sulfide,
- silver(I) chloride,
- silver(I) bromide (also shows Schottky defects),
- silver(I) iodide.
What is metal deficiency defect give example?
e.g., Transition metal compounds like NiO, FeO, FeS etc. By having extra anion occupying interstitial site: In this, an extra anion is present in the interstitial position. The extra negative charge is balanced by one extra positive charge on the adjacent metal ion.
What are imperfections in solids?
Any irregularity in the pattern of crystal arrangement in a solid lattice is called imperfection in solids. The occurrence of defects takes place when crystallization (the process of formation of crystals) occurs at a very fast or at an intermediate rate.
Which crystals show Frenkel defect and why?
Frenkel defect is occurred in those ionic crystals in which sizes of ions (anions and cations) show large differences. Compounds such as KCl, KBr, CsCl etc. show Schottky defect. Compounds such as NaCl, ZnS, AgI etc.
Which of the following defects decrease the density?
Vacancy and Schottky defect which lead to decrease the density both are the types of a stoichiometric defect. In case of Frenkel defect and interstitial defect, there is no change in density of substance.
Which one of the following defects does not affect the density of solids?
Frenkel defect does not change the density of the ionic crystal whereas, Schottky defect lowers the density of ionic crystal.
Which crystal shows both Schottky and Frenkel defect?
AgBr
What shows Schottky effect?
It occurs in highly ionic compounds with high coordination number and mostly when the cation and the anion are of comparable size i.e. little difference between cation and anion size. Examples of crystals showing Schottky defect are NaCl, KCl, KBr, CsCl etc.
Which type of ionic substances shows Frenkel defect?
Frenkel defects are mostly exhibited in ionic solids where the smaller ion (usually the cation) is dislocated. Some examples include AgBr, ZnS, AgCl, and AgI.
What is Frenkel defect what is its effect on the density of a solid?
In this defect, a cation (or an anion) is dislocated from its normal site to interstitial site. Interstitial site is the place between the lattice sites. This defect is observed in solids when the difference in ionic radii of two participating ions is large. Density is not affected due to this defect.