Which is the incorrect statement ?

Options

A. ` FeO_(0.98)` has non-stoichiometric metal deficiency defect
B. Density decreases in case of crystals with Schottky's defect
C. NaCl (s) insulator , silicon is semiconductor, silver is conductor, quartz is piezoelectric crystal
D. Frenkel defect is favoured in those ionic compounds in which the sizes of cations and anions are almost equal

Explanation

Non-stoichiometric ferrous oxide is ` Fe_(0.93 - 0.98) O_(1.00) ( and "not" FeO_(0.98))` which is due to metal deficiency defect. Hence, (a) is inorrect . Fernkel defect is favorured in those ionic compounds in which sizes of cation and anion are largely different. Hence, (d) is incorrect .