Question

A cation vacancy and an anion vacancy in a crystal is called

• A. Frenkel defect
• B. Schottky defect
• C. Dislocation
• D. Surface imperfection

Hint:

Schottky defects are prevalent in ionic solids where both cations and anions are removed in equal numbers. This results in a decrease in crystal density, and since the removal of ions is balanced, electrical neutrality is preserved.

Answer 1

The Correct Option is B

A Schottky defect occurs in ionic crystals when both a cation and an anion are displaced from their respective lattice positions, creating vacancies for both particles. This type of defect results in a pair of vacancies, which leads to a reduction in the overall density of the crystal. Schottky defects are commonly found in crystals of ionic compounds with similar-sized cations and anions, such as sodium chloride (NaCl), potassium chloride (KCl), and cesium chloride (CsCl). Schottky defects help maintain electrical neutrality in the crystal because they involve the equal loss of both cations and anions. However, as a result of the vacancies, the crystal may exhibit some changes in its physical properties, such as a reduction in density due to the missing ions. This type of defect can also impact the crystal's electrical conductivity, as the missing ions can affect the movement of charge carriers.