Effects of Ce substitution on the structural and electromagnetic properties of NiZn ferrite

NiZnCe ferrite, Ni_0.4Zn_0.6−xCe_xFe₂O₄ (0 ≤ x ≤ 0.20), were prepared by the sol-gel self-spreading process combing with the solid reaction process. The crystal structure and physical properties of NiZnCe ferrite with different amount of Ce substitution have been studied. The lattice parameter and density rise and the grain size is decreasing with Ce substitution increasing because the ionic radius of Ce³⁺ ion is much bigger than that of Zn²⁺ ions, and the atomic weight of Ce³⁺ ions is heavier than Zn²⁺ ions. Ms initially increases with increasing amount of Ce substitution because of the increase of density and reduction of porosity, then it decreases when Ce substitution excesses 0.15 which contributes to the increase of the net magnetic moment in tetrahedral site and porosity and the apparence of CeO₂ phase. Hc monotonously decreases with Ce substitution increasing due to the mono-domain structure of grains. The initial permeability initially increases at room temperature with the Ce substitution content increasing and has the maximum when the replacement content is 0.15. But it sharply drops when the amount of Ce replacement is 0.20 because the porosity increasing and impurity phase appearance. The Curie temperature has been greatly improved with Ce substitution due to the enhancements of A-B superexchange interactions. The dc resistivity gradually decreases at room temperature due to the fact that Ce substitution reduces the activation energy, and it obeys an exponential decay with the temperature increasing.