Fig. 1 shows the variation of the relative intensity I2, and the lifetime τ2 with the ionic radii of the substituted ions for Li-ferrite. It is noticed that I2 mostly increases with the ionic radii of the substitution ions, and then decreases for Sm Li-ferrite sample. This defect is the sum of nanoscale grain boundaries thickness and intergranular pores. ( Table 1) indicates the increase of the average grain size with increasing the ionic radii of substituted ions. Similar result was reported for Mn–Zn ferrite [19].