AIIMS2017ChemistrySolid State
ZnO is white when cold and yellow when heated. It is due to the development of
Options
- AFrenkel defect
- Bmetal excess defect
- CSchottky defect
- Dmetal deficiency defect.
Correct answer
B. metal excess defect
Step-by-step solution
ZnO turns yellow on heating as Zn ²⁺ ions move in interstitial sites and electrons also get entrapped in nearby interstitial sites to maintain electrical neutrality. As extra Zn ²⁺ ions are present in interstitial sites thus, it is metal excess defect.