What is Schottky defect in case of ionic crystal?

Schottky. In elemental crystals it refers to simple lattice vacancies, also called valency defects. 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 types of defects is observed in ionic crystals?

Imperfections or defects in crystalline solid can be broadly classified into four groups, namely, point defect, line defect, surface defect and volume defect.

What happens in Schottky defect?

In the so-called Schottky defect, an atom moves from the inside of the crystal to its surface, leaving behind an isolated vacancy. In the Frenkel defect, an atom moves to a new position between other atoms of the solid.

What is Schottky and Frenkel defect?

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 and Frenkel defect 12?

Schottky defect is occurred in those crystals in which sizes of ions is almost similar. 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.

What are Schottky and Frenkel defect?

Is Schottky defect stoichiometric?

Both Frenkel and Schottky defects are stoichiometric defects.

How does Frenkel defect occur in ionic crystal?

a. Frenkel defect arises when an ion of an ionic compound is missing from its regular lattice site and occupies an interstitial position between lattice points. The cations are usually smaller than anions. The smaller cation is displaced from its normal site to interstitial space.

What is the Schottky defect in a crystal?

The Schottky defect is a point defect in which both cation and anion remain missing from the lattice site in equal numbers. Due to this defect, a decrease in the density of the crystal can be observed. The Schottky defect is found in the highly ionic compounds with having cations and anions of the same sizes.

How does Schottky’s defect affect the density of ionic compounds?

Schottky defect reduces the density of ionic compounds because a fraction of ions leaves the crystal, hence reducing the overall mass at the same crystal volume.

Why do potassium and chlorine show Schottky defects?

Potassium (K) has an atomic number of 19 and Chlorine (Cl) has an atomic number of 17. Both the ions are of similar size, and hence it is a good candidate for showing Schottky defects. Schottky defects usually occur when heat is applied to the ionic compound crystal. Heat raises the temperature, and hence the thermal vibration within the crystal.

What is the difference between lattice vacancy defect and Schottky defect?

Typically, when the defect is found in non-ionic crystals it is referred to as lattice vacancy defect. Schottky defect is however different from frenkel defect wherein the atoms permanently leave the crystal in terms of schottky defect while atoms usually stay within the solid crystal in frenkel defect.