Explain the following terms with suitable examples: (i) Schottky defect (ii) Frenkel defect (iii) Interstitials and (iv) F-centres
(i) Schottky disorder: Schottky illness is essentially a emptiness illness proven via way of means of ionic solids. In this disorder, an equal range of cations and anions are lacking to hold electric neutrality. It decreases the density of a substance. Significant quantity of Schottky defects is found in ionic solids. For example, in NaCl, there are approximately 10 6Schottky pairs according to cm3at room temperature. Ionic materials containing similar-sized cations and anions display this form of illness. For example: NaCl, KCl, CsCl, AgBr, etc.(ii) Frenkel disorder: Ionic solids containing big variations withinside the sizes of ions display this form of disorder. When the smaller ion (typically cation) is dislocated from its ordinary web website online to an interstitial webweb page, Frenkel illness is created. It creates a emptiness disorder in addition to an interstitial disorder. Frenkel illness is likewise called dislocation disorder. Ionic solids such as AgCl, AgBr, AgI, and ZnS display this kind of disorder.(iii) Interstitials: Interstitial disorder is proven via way of means of non-ionic solids. This kind of disorder is created whilst a few constituent particles (atoms or molecules) occupy an interstitial web website online of the crystal. The density of a substance will increase because of this illness.(iv) F-centres: When the anionic webweb sites of a crystal are occupied with the aid of using unpaired electrons, the ionic webweb sites are referred to as F- centres. These unpaired electrons impart coloration to the crystals. For example, while crystals of NaCl are heated in an environment of sodium vapour, the sodium atoms are deposited at the floor of the crystal. The Cl ions diffuse from the crystal to its floor and integrate with Na atoms, forming NaCl. During this process, the Na atoms at the floor of the crystal lose electrons. These launched electrons diffuse into the crystal and occupy the vacant anionic webweb sites, developing F-centres.
