ZnO shows yellow colour on heating due to

Options

A. Frenkel defect
B. Metal excess defect
C. Metal deficiency defect
D. Schottky defect.

Answer

B

Explanation

Zinc oxide is white in colour at room temperature. On heating it loses oxygen and turns yellow.
`ZnOoverset("Heating")rarrZn^(2+)+(1)/(2)O_(2)+2e^(-)`
Now there is excess of zinc in the crystal and its formula becomes `Zn_(1+x)O`. The excess `Zn^(2+)` ions move to interstitial sites and the electrons to neighbouring interstitial sites.