The influence of aluminum’s crystalline structure on the elastic, dielectric, and electrical properties of Ni ferrite

Abstract

The authors investigate the effect of Al on the structural, elastic, and electrical properties of a Ni nano ferrite. Six samples of NiAlxFe2-xO4 (where x= 0.00, 0.20, 0.40, 0.60, 0.80, and 1.00) were synthesized using flash auto combustion. As shown in XRD patterns, the lattice appears as a Fd-3m space group, a single-phase spinel structure with average crystallite size ranging from 22.4 - 24.7 nm for all samples. SEM and TEM images showed a uniform and spherical structural with a narrow size distribution. The results manifest significant changes in the elastic and electrical properties due to the presence of Al. As Al content increased, the bulk B, shear G, and Young E moduli decreased and remained in the same order of hundreds in the GPa range: however, the values of the Debye temperature θD increased. The dielectric parameters ε′, ε″, and tan δ decreased as the frequency of the applied field and Al content increased: they also decreased as temperature increased. The relaxation times were τ_ε=τ_tanδ=0.1959 μs for all samples. The electric moduli M′ and M″ increased as the frequency of the applied field and Al content increased, but they decreased as temperature increased. The relaxation times are dispersed depending on Al content, frequency, and temperature. The Cole-Cole curve showed two semicircles corresponding to the grain and grain boundary with the electrical relaxation of the non-Debye form. The electric impedance Z′ and Z″ increased as the frequency of the applied field and temperature increased, although they decreased as Al content increased. These results indicate that Ni-Al ferrite has respectable dielectric properties, which opens the door for many applications in control and safety monitoring tools, where dynamic process temperature sensors are of great importance and the temperature dependency of the material is significant.