When zinc oxide is heated strongly above 800-degree celcius, it turns yellow. After cooling down, the colour of zinc oxide changes back to white. Thus, it is a reversible process. The hot zinc oxide absorbs the blue wavelength of light, and thus, the reflected light is observed as yellow.
- In ZnO, the ions of Zn2+ occupy the interstitial sites and electrons are trapped in the interstitial sites because of neutralization.
- The colour of zinc oxide is white at room temperature, whereas on heating, it turns yellow due to loss of oxygen reversibly at .very high temperatures