Question:
The white $ ZnO $ turns yellow on heating because of
The white $ ZnO $ turns yellow on heating because of
Updated On: Aug 15, 2022
- Frenkel defect
- Metal excess defect
- Metal deficiency defect
- Schottky defect
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The Correct Option is B
Solution and Explanation
$ZnO$, on heating, loses oxygen and thus, the zinc metal becomes in excess in $ZnO$ crystal. Hence, the formula of $ZnO$ becomes $Zn_{1+x}O$ The excess $Zn^{2+}$ ions move to interstitial sites and the electrons to neighbouring interstitial sites. The electrons are responsible for the yellow colour of $ZnO$
$ZnO { ->[\Delta] } Zn^{2+}+\frac{1}{2}O_{2}+2e^{-}$
Thus, yellow colour of $znO$ is due to metal excess defect
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Concepts Used:
Solid State
Solids are substances that are featured by a definite shape, volume, and high density. In the solid-state, the composed particles are arranged in several manners. Solid-state, in simple terms, means "no moving parts." Thus solid-state electronic devices are the ones inclusive of solid components that don’t change their position. Solid is a state of matter where the composed particles are arranged close to each other. The composed particles can be either atoms, molecules, or ions.
Types of Solids:
Based on the nature of the order that is present in the arrangement of their constituent particles solids can be divided into two types;
- Amorphous solids behave the same as super cool liquids due to the arrangement of constituent particles in short-range order. They are isotropic and have a broad melting point (range is about greater than 5°C).
- Crystalline solids have a fixed shape and the constituent particles are arranged in a long-range order.