Solid Solution

Solid solutions are formed by mixing two solid components. Alloys (mixtures of metals) are the examples of solid solutions.

Solid solutions can be classified under two types:

a) Substitutional solid solutions

b) Interstitial solid solutions.

In substitutional solid solutions atoms, molecules or ions of one substance take place of particles of another substance in a crystalline lattice as shown in the figure.

fig 3.1

Example: Sulphides of zinc and cadmium form such mixtures in which cadmium ions randomly replace zinc ions in the ZnS crystal lattice. Another example is brass where copper and zinc atoms are randomly arranged in the lattice structure.

In interstitial solid solutions the atoms of one substance is present in the voids or interstices that exists in the lattice structure of the other substance, which is called the host lattice.

fig 3.2

Example: Tungsten carbide, WC, the tungsten atoms are arranged in a face - centered cubic pattern with carbon atoms in octahedral holes. It is an extremely hard substance, which has many industrial use.

Example: Cutting tools