In an ideal crystal, the entropy of the constituents at absolute zero temperature (0K) is zero. However, the crystals generally suffer from certain defects also called imperfections They may be both electronic and atomic in nature. The atomic imperfections may be stoichiometric (Schottky and Frenkel defects) or non-stoichiometric (metal excees and metal deficiency defects). In addition to these, there are impurity defects which are caused by the addition of certain impurities of metals and this is known as dopping. The dopping leads to semi conductors which may be either n-type or p-type in nature.
Zinc oxide (ZnO) is white when cold and yellow when hot. It is due to the development of :
A. Frenkel defect
B. Schottky defect
C. Metal excees defect
D. Metal deficiency defect
