Study the Properties of Cu-Zn Ferrite Substituted with Rare Earth Ions by Using Positron Annihilation Analysis

Positron annihilation lifetime spectroscopy (PALS) is a direct probe of size and concentration of nano-scale defects in materials, because it is very sensitive to electron density. The lifetime of positron (τ) and its intensity (I) can be used to characterize the defects concentration. In the present work, PALS has been applied to measure the variation of positron lifetime parameters for polycrystalline samples with chemical formula Zn0.5Cu0.5Fe1.98R0.02O4 (R = Gd, Sm, Nd and La). The variation of positron annihilation lifetime parameters (I1, I2, τav and k) with the ionic radius of rare earth ions, homogeneity, grain size and electrical resistivity have been studied. The inter-granular pores and grain boundaries defects are increased with the increasing of the ionic radius of the rare earth ions and decreased for Gd-sample. The defects inside and outside the grains are distributed homogeneously for Sm-sample only. A positive correlation has been found between positron lifetime parameters and ionic radius of rare earth ions as well as the electrical resistivity.