As the position of the peaks in the XRD patterns depends on the lattice parameters of the unit cell. When the unit cell parameters increases peak shifted towards lower side and vice versa. Since the lattice parameters also depend on particle size, so, we observes shift in peak position. In some systems peak shifted towards lower angle side and in some systems towards higher angle side. In lower case, there is an increment in lattice parameters with lowering particle size to nanometer.