What is the Difference Between Substitutional and Interstitial Solid Solution?

The main difference between substitutional and interstitial solid solutions lies in the way the solute atoms are incorporated into the crystal structure of the solvent atoms:

• Substitutional Solid Solution: In this type of solid solution, the solute atoms replace some of the solvent atoms in the crystal structure. The atomic size of solutes is nearly similar to the size of solvent atoms, and there is displacement of solvent atoms by solute atoms. This type of solid solution forms only if the solute atoms are large enough to replace the solvent atoms.
• Interstitial Solid Solution: In an interstitial solid solution, the solute atoms fill some of the holes between solvent atoms in the crystal structure. The atomic size of solute atoms should be about 40% of the size of solvent atoms in order to form this type of solid solution. The solute atoms enter the holes between solvent atoms without displacing them.

In summary, the key difference between substitutional and interstitial solid solutions is the way solute atoms are incorporated into the solvent atoms' crystal structure, either by replacing solvent atoms (substitutional) or by filling the holes between solvent atoms (interstitial).

Comparative Table: Substitutional vs Interstitial Solid Solution

The key difference between substitutional and interstitial solid solutions lies in the way they form. Here is a comparison between the two types of solid solutions:

Both substitutional and interstitial solid solutions are formed when one or more solutes are dissolved in a solvent in the solid state, resulting in a resultant crystal structure with enhanced properties such as strength. The choice between substitutional and interstitial solid solutions depends on the size and atomic properties of the solute and solvent atoms.