The dependence of the relative intensity I1 with the ionic radii for the samples with substitution 1% is in opposite behavior relative to these samples with 2% substitutions ( Fig. 6). So, for samples with substitution 1%, the intragranular defects increase with the ionic radii which cause the un-homogeneity for these samples. This behavior cannot be explained according to the cations distribution between A-sites and B-sites of the crystalline structure of spinel ferrite. This reverse behavior may attribute to the growth of the samples. Samples with substitution 2% grow slower than the samples which are substituted with 1% under the same preparation condition. Another factor for the un-homogeneity for 1% substituted samples is the formation of Fe2+ ions. It is reported that Fe2+ ions are formed during the preparation condition for ferrites [8]. The concentration of these ions could be greater for samples substituted with 1% than that substituted with 2%. Although, I1 and τ1 have nearly the same behavior but reversed for both substitution x = 1% and 2%, they still have the same consideration, ( Fig. 6 and Fig. 7). The lifetime of positron increases with increasing the concentration of intragranular defects inside the samples due to the decrease of the hopping of the electrons.