Which of the following statements regarding crystal defects is not correct?

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If $NaCl$ crystals are doped with ${Al}^{+ 3}$ tons, then 3 cationic vacancies will be generated per ${Al}^{3 +} .$ inserted.

Schottky defects are type of vacancy defects.

Packing fraction remains unaffected in Frenkel defects.

Addition of $As$ in $Si$ results in formation of $n - type$ semiconductor.

answer is B.

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Detailed Solution

(A) The absence of an equal amount of cations and anions from a crystal lattice results in the formation of Schottky defects. Dislocation defects are often referred as as Frenkel defects. Therefore, this assertion is false.

(b) Two cation vacancies are produced when ${Al}^{3 +}$ is added to $NaCl$ . The crystal lattice now bears ${Na}^{+ 2}$ charge after one ${Na}^{+}$ was replaced with an ${Al}^{3 +}$ . Only two vacancies are produced because only two ${Na}^{+}$ ions need to be eliminated in order to preserve electroneutrality.

(c ) Because As has one extra valence electron than Si, it can be added to Si to produce n-type semiconductors.

d) The packing fraction measures the percentage of a crystal structure's volume that is occupied. Therefore, packing fraction declines as a result of the vacancy defect.

hence option (b) is incorrect

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