Eff'ect of Lanthanum Substitution on the Structural, Magnetic and Transport Properties of Cu-Zn Ferrites

Abstract

This thesis work is acquainted with the study of lanthanum (La) doped Cu-Zn ferrite. The composition of the sample is Cu0.15Zn0.85LaxFe2-xO4 where it was prepared for x = 0.00, 0.02, 0.04, 0.06 and 0.08 content of La by Solid State Reaction method. The samples were pre-sintered at 800oC for 3hours and sintered at 1150oC for 3 hours. The substitution of La for various ratio have remarkable effects on the structural, magnetic and electrical properties of Cu-Zn ferrite. The phase identification has carries out by using X-ray diffraction (XRD). The XRD analysis revealed that undoped in Cu-Zn ferrite shows formulation of cubic single phase (fcc) spinel structure without any impurity peak but other four La doped Cu-Zn ferrites are shows additional peaks manifested the formation of secondary phase presumably LaFeO3. The values of lattice parameter have the trend of increasing with the increase of x. The bulk density also has a trend of increasing with the increase of La content where the X-ray density decreases. In morphological study, SEM image exhibit uniform surface morphology with well defined spherical grain. The average grain size was calculated using Image J Software and it was observed that, the average grain size decreases with increasing La content. The magnetic properties were studied by investigating M-H curves that was obtained by vibrating sample magnetometer (VSM). The magnetic properties demonstrated a strong dependence of the variation of x. With the increase of x, saturation magnetization (Ms) decreases while remanent magnetization (Mr) and coercivity (Hc) increases. The hysteresis curve for samples of various ratio of La showed the ferromagnetic behavior. The decrease of Ms with increasing of La substitutions has been explained as the effect of dilution of Fe3+ magnetic moment by nonmagnetic La3+. The complex permeability, loss tangent, dielectric properties were investigated as a function of frequency upto 120MHz by using impedance analyzer. The initial permeability slightly increases with the increase of La substation while imaginary permeability decreases. Moreover the dielectric constant decreases rapidly with the increase in frequency at lower frequencies and slowly at higher frequency and almost constant exhibiting normal behavior of ferrites. Dielectric constant decreases with increases of La content in Cu-Zn ferrites. The electrical DC resistivity has a trend of increasing with the increase of La content. The variation of electrical and dielectric in La doped Cu-Zn ferrites are explained on the basis of Fe2+/Fe3+ ionic concentration with affect La ions as well as the electronic hopping frequency between Fe2+ and Fe3+ ion.