what type of stoichiometric defect is shown by zns and agbr

question : what type of stoichiometric defect is shown by (i) zns and (ii) agbr

key points to remember answer this question : First of all you have to remember that there is very big difference between zns and agbr on the basis of size of ions present in zns and agbr so first we have to think which type of defect can occur on the basis of size of ions. Then also remember the exceptional behavior of AgBr. remember frenkel defect occurs in ionic solids when large difference is found among the size of ions. and when the difference is low then between the cation and anion Schottky Defect can be seen.

solution :  (i) zns : ZnS shows Frenkel Defect , the reason is , the ions of ZnS have large difference among it’s ions. hence on the basis of big difference between the ions the Frenkel Defect occurs.

(ii) Agbr : In AgBr shows both type of defects means frenkel defect and schottky defect both found in AgBr because of size difference and also the exceptional behavior of AgBr.

In short –

(i) zns : Frenkel Defect

(ii) Agbr : frenkel defect and schottky defect