Question

(a) Identify the non – stoichiometric defect 

(i) Schottky defect

(ii) Frenkel defect

(iii) Interstitial defect

(iv) Metal deficiency defect

(b) What type of substance could make better permanent magnets – ferromagnetic or ferrimagnetic? Justify your answer.

(c) In terms of Band theory write the differences between conductor and insulator.

Answer 1

(a) iv) Metal deficiency defect

(b) Ferromagnetic substances could make better permanent magnets because when these substances are placed in a magnetic field all the magnetic moments (domains) get oriented in the direction of the magnetic field and a strong magnetic effect is produced. This ordering of domains persist even when the magnetic field is removed and the ferromagentic substance becomes a permanent magnet.

The schematic alignment of magnetic moments in a ferromagnetic substance is as shown below:

(c) In conductors the valence band is either partially filled or it is overlaped with a higher energy unoccupied conduction band so that the electrons can flow easily under an applied electric field. Whereas in insulators the energy gap between the filled valence band and the next higher unoccupied conduction band is large so that electrons cannot jump to it.