1.1 Brief Review of Structure of Materials

In the following sections, we will quickly look at the concepts of lattice, unit-cell and crystal structures which will be useful to understand the crystal structures of common ceramic compounds.

1.1.1 Point Lattice

In a point lattice, the following characteristics are obeyed:

• There is a periodic arrangement of points in space. (Figure 1.1(a))
  

• In addition, each point must have identical neighbourhood.(Figure 1.1(b))

Lack of regular arrangement No periodicity Non-identical neighbourhood	Regular arrangement Periodicity Identical neighbourhood of each point