Here's why:
* Schottky Defect: This defect involves the absence of an atom or ion from its normal lattice site, creating a vacancy. This vacancy is essentially an empty space within the crystal structure.
* Volume Change: When a vacancy is formed, the overall volume of the crystal slightly decreases. This is because the missing atom or ion is no longer contributing to the overall volume occupied by the crystal.
The extent of volume change depends on:
* Concentration of Defects: The higher the concentration of Schottky defects, the greater the volume reduction.
* Nature of the Crystal: The specific crystal structure and the size of the missing atom or ion will influence the magnitude of the volume change.
Important Note: The volume change due to Schottky defects is usually very small and difficult to measure directly. However, it can be observed indirectly through changes in density or other physical properties.
