Effects of sintering temperature on microstructure, initial permeability and electric behaviour of Ni-Mn-Zn ferrites

Abstract

The effects of sintering temperature on microstructure, initial permeability, and electrical behaviour of Ni sub(0.5-x) Mn sub(x) Zn sub(0.5) Fe sub(2) O sub(4) (0.0 less than x less than 0.5) prepared using the precursor combustion method have been investigated. X-ray diffraction analysis confirmed the single phase cubic spinel structure of Ni sub(0.5-x) Mn sub(x) Zn sub(0.5) Fe sub(2) O sub(4) (0.0 less than x less than 0.4) compositions sintered at 1100 degrees C. The Mn sup(2+) substituent preferentially occupies tetrahedral sites as indicated by the Rietveld analysis and the increase in the IR absorption frequency of Nu sub(1) band with increasing Mn substitution. The SEM measurements have revealed homogeneous microstructures of the ferrites with narrow grain size distribution in the range 0.93 Mu m-1.86 Mu m. Mossbauer spectra exhibit a superposition of two Zeeman sextets for the compositions x less than or equal to 0.2, a superposition of two Zeeman sextets, and a paramagnetic doublet for the compositions, x = 0.3 and 0.4, and one sextet and single quadrupole doublet for a composition, x = 0.5. The activation energy in the range 0.258 eV-0.612 eV suggests a polaron hopping type conduction mechanism in all the sintered ferrites. The dielectric constant in the range 0.057-55.21 and lower dielectric loss (10 sup(-2)) imply better stoichiometry and homogeneity. The initial permeability increases at lower Mn substitution (x = 0.2) and exhibits a decrease as the Mn substitution increases. The dc resistivity, dielectric constant, and initial permeability values suggest the suitability of these ferrites for high frequency device applications.