Frenkel defect is generally observed in which of the following?

As a result of Schottky defect,the density of the crystal:

If an electron is present in place of an anion in a crystal lattice,then it is called

The formula of a metal oxide with a metal deficiency defect in its crystal is $A_{0.8}O$. The crystal contains $A^{2+}$ and $A^{3+}$ ions. The fraction of metal existing as $A^{2+}$ ions in the crystal is -

Experimentally,it was found that a metal oxide has the formula $M_{0.98}O$. The metal $M$ is present as $M^{2+}$ and $M^{3+}$ in its oxide. The fraction of the metal which exists as $M^{3+}$ would be: .................... $\%$

Schottky defect in a crystal arises due to