Effect of rare earth oxides and La3+ ion concentration on some properties of Ni–Zn ferrites

Abstract

The effect of both the rare earth ions and the La3+ ion concentration on the dielectric properties of Ni0.5Zn0.5RyFe2−yO4; 0.0≤y≤0.9, R=La, Yb, Dy and Ce is studied. All the samples are sintered at 1250°C with heating rate of 4°C/min and sintering time of 35h. The ionic radii of the used rare earth (Yb3+, Dy3+, Ce3+ and La3+) are too large to occupy the octahedral site. They form a secondary phases on the grain boundaries. The X-ray data shows that the lattice parameter for the un- substituted ferrite sample is larger than the substituted one, which is the main feature for all rare earth elements. The dielectric properties show that the pure sample has a larger dielectric constant as well as a larger valence exchange with respect to substituted one. This means that introducing rare earth ions into the samples decreases ε′ owing to the decreasing Fe–Fe interaction.The lowest conduction for La substituted sample is attributed to the nature of La3+ ions which is insoluble in the spinel lattice so it hindered Fe–R (3d–4f) coupling. This feature can help to obtain well applicable ferrites.