Electron-deficient impurities are caused by the elements of which group?

Which of the following compounds is likely to show both Frenkel and Schottky defects in its crystalline form?

In spite of long-range order in the arrangement of particles,why are the crystals usually not perfect?

$A$ silicon specimen is made into a $p-$type semiconductor by doping,on an average,one indium atom per $5 \times 10^7$ silicon atoms. If the number density of atoms in the silicon specimen is $5 \times 10^{28} \ \text{atoms} \ m^{-3}$,then the number of acceptor atoms in silicon per cubic centimeter will be

At what temperature will the Schottky defect be maximum?

An example of a non-stoichiometric compound is