devarshi-dt-logo

Question:

ZnO is white when cold and yellow when heated. It is due to development of:

metal excess defect

Schottky defect

Frenkel defect

metal deficiency defect

Solution:

ZnO turns yellow on heating as Zn2+ ions move in interstitial sites and electrons also get entrapped in nearby interstitial sites to maintain electrical neutrality. As extra Zn2+ ions are present in interstitial sites thus, it is metal excess defect.