What is Frenkel Defect ?

The defect present in the compounds having fixed composition are called stoicheometric defect. Two type of defects may be observed in stochiometric compounds, called schottky and frenkel defects.

  FRENKEL DEFECT   

 A Frenkel defect consists of a vacant lattice site (a 'hole), and the ion which ideally should have occupied the site now occupies an interstitial positive (see image)


Metal ions are generally smaller than the anions. Thus it is easier to squeeze A into alternative interstitial positions, and consequently it is more common to find the positive ions occupying interstitial position. This type of defect is favoured by a large difference in size between the positive and negative ions. eg. ZnS, Agel, Agl etc.

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