Imperfection in Solids
Imperfection in Solids: Overview
This topic covers concepts such as Imperfections in Crystalline Solids, Point Defects and Line Defects, Types of Point Defects, Stoichiometric Defects, Non-Stoichiometric Defects, Impurity Defects, Vacancy Defects, Interstitial Defects, etc.
Important Questions on Imperfection in Solids
Which of the following ionic compound will show Frenkel defect?
Which of the following point defect of crystals decreases the density of a solid?
In a solid lattice, the cation has left a lattice site and is located at an interstitial position The lattice defect is
Schottky defect in crystals is observed when
Match the following:
| Column I (Defect) | Column II (Effect) |
| (A) Schottky defect | (p) Crystal becomes coloured |
| (B) Doping silicon with aluminium | (q) n-type semiconductor is formed |
| (C) Doping silicon with arsenic | (r) p-type semiconductor is formed |
| (D) Heating crystal in presence of sodium vapour | (s) Density of the crystal decreases |
No crystal is found to be prefect at room temperature. The defects present in the crystals can be stoichiometric or non-stoichiometric. Due to nonstoichiometric defects, the formula of the ionic compound is different from the ideal formula. For example, the ideal formula of ferrous oxide should be but actually in one sample, it was found to be . This is because the crystal may have some ferric ions in place of ferrous ions. These defects change the properties of the crystals. In some cases, defects are introduced to have crystals of desired properties as required in the field of electronics. Doping of elements of Group 14 with those of Group 13 or 15 is most common. In ionic compounds, usually impurities are introduced in which the cation has higher valency than the cation of the parent crystal, e.g., into .
Which one of the following defects does not affect the density of the crystal ?
No crystal is found to be prefect at room temperature. The defects present in the crystals can be stoichiometric or non-stoichiometric. Due to nonstoichiometric defects, the formula of the ionic compound is different from the ideal formula. For example, the ideal formula of ferrous oxide should be but actually in one sample, it was found to be . This is because the crystal may have some ferric ions in place of ferrous ions. These defects change the properties of the crystals. In some cases, defects are introduced to have crystals of desired properties as required in the field of electronics. Doping of elements of Group 14 with those of Group 13 or 15 is most common. In ionic compounds, usually impurities are introduced in which the cation has higher valency than the cation of the parent crystal, e.g., into .
was doped with . The concentration of cation vacancies is
For the number of Schottky pairs per at room temperature are
Identify the incorrect statement regarding crystals having Frenkel defect:
Non-stoichiometric cuprous oxide, Cu2O can be prepared in laboratory. In this oxide, copper to oxygen ratio is slightly less than 2 : 1. This substance is a?
Which is/are incorrect for Schottky defect in rock salt type crystals:
Which one of the following has both Schottky and Frenkel defects?
Transition metals show variable _____ states. Moreover, they have vacancies present in their metal lattice. Thus, they form interstitial compounds.
How are the properties of crystals affected by Schottky and Frenkel defects? Electrical conductivity
How are the properties of crystals affected by Schottky and Frenkel defects? Density
What type of defect is shown by and why?
Which non-stoichiometric point defect responsible for colour in alkali metal halides?
Which point defects in its crystal units alters the density of a solid?
