Among the following solids,Schottky defect is $NOT$ observed in-

At what temperature will the Schottky defect be maximum?

The correct statement among the following,regarding defects in solids is:
$(1)$ Frenkel defect is favored by small difference in the sizes of cation and anion.
$(2)$ Frenkel defect is a metal excess defect.
$(3)$ Trapping of electron in the lattice leads to formation of $F$-centres.
$(4)$ Schottky defect has no effect on the physical property of solids.

Use the appropriate symbols $T$ (True) or $F$ (False) for the following statements regarding defects in solids:
$(1)$ Frenkel defect arises due to the arrangement of cations and anions with a very small difference in size.
$(2)$ Frenkel defect can be called a dislocation defect.
$(3)$ $F$-centers arise due to the migration of electrons released from metal atoms into the crystal lattice.
$(4)$ Physical properties of the crystal do not change due to Schottky defect.

Due to the Frenkel defect,the density of a solid $..........$

In an ionic crystal,$F$-centers are.....