question_answer 72)

  Which of the following point defects are shown by AgBr(s) crystals?          1. Schottky defect                                                           2. Frenkel defect                                                              3. Metal excess defect                                                        4. Metal deficiency defect                                                       (a) 1 and 2                           (b) 3 and 4        (c) 1 and 3                           (d) 2 and 4          

Answer:

                  (a) AgBr shows both Schottky as well as Frenkel defect. In AgBr, both Ag'1' and Br ions are absent from the lattice causing Schottky defect. However, Ag'1' ions are mobile so  they have a tendency to move aside the lattice and trapped in interstitial site hence, cause Frenkel defect.