THE EFFECT OF IRON CONCENTRATION ON THE STRUCTURAL, ELECTRICAL, MAGNETIC AND MAGNETOELECTRIC PROPERTIES OF MULTIFERROIC COMPOSITES

Abstract

In this dissertation, stoichiometric and non-stoichiometric nickel copper zinc ferrites and ferroelectromagnetic composite ceramics (FEMCCs) have been synthesized. Crystal structure, micromorphology, elastic, electric, and magnetic traits of stoichiometric and non-stoichiometric nickel copper zinc ferrites and phase structure, micromorphology, electromagnetic and magnetoelectric traits of FEMCCs have been investigated employing X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), Scanning electron microscope (SEM), Vibrating sample magnetometer (VSM), and Impedance analyzer. Stoichiometric Ni0.25Cu0.13Zn0.62Fe2O4 (NCZFO) ceramics were prepared adopting the solid-state reaction approach and annealed for 5h at various sintering temperatures (Ts). FTIR and XRD analyses reveal that the development samples possessed spinel skeleton cubic symmetry. Micromorphological (SEM) study revealed that the grain size increases with increasing Ts. The longitudinal, transversal, and mean elastic wave velocities, elastic moduli, Poisson ratio were estimated using FTIR data. The electric permittivity increases with Ts due to the partial transformation of Fe3+ to Fe2+, and exhibits dispersive character due to interfacial polarization. Electrical conduction mechanism follows Jonscher’s law and is governed by the small polaron hopping phenomenon. The magnetic permeability boosts with increasing Ts due to the enhancement in bulk density as well as grain diameter. The Q-factor declines while the frequency of resonance moves toward low frequency region with Ts. The magnetic traits exceedingly decline with increasing Ts due to the lack of sample’s homogeneity and existence of intra-granular porosity. Ni0.25Cu0.13Zn0.62Fe2-xO4-3x/2 (NCZFe2-xO4-3x/2) (x = 0.0; 0.04, 0.08; 0.12) ceramics were developed using the traditional solid state synthetic process and annealed for 5h at various Ts. XRD study ascertained the development of the spinel skeleton without having no detectable undesired phases. The lattice constant escalates in a linear fashion with iron-deficient non-stoichiometry (IDNS) content at 1100 ℃, while it alters non-systematically at 1150, 1200, and 1250 ℃. The elastic moduli, Poisson’s ratio, longitudinal, transversal, and mean elastic wave velocities have been determined using FTIR data. According to SEM study, the magnetic interplay in the midst of the component grains causes abnormal and agglomerated grain development. The enhanced densification and production of Fe2+ ions result in an enhancement in the dielectric characteristics on increasing the temperature of sintering. The investigation of ac electrical conductivity indicated that a small-polaron-based hopping mechanism governs the conduction process. Nyquist plots suggested that the effect of the grain border is mainly is responsible for electrical conduction in non-stoichiometric nickel copper zinc ferrites rather than grain. According to the amount of IDNS, changes in density, porosity, grain diameter, and magnetic anisotropy may be responsible for the observed alternations in magnetic permeability and magnetic loss tangent. (1-y) [BCZTO] + (y) [NCZFO] (0 ≤ y ≤ 1.0) FEMCCs were developed using the solid state reaction approach and annealed for 5h at various Ts. XRD and FTIR examinations reveal that no impurity phases formed during the production of the single-phasic NCZFO spinel skeleton and the BCZTO tetragonal perovskite. SEM investigation revealed that a quasi-spherical type microstructure with low voids or pores, insignificant aggregation, and reasonably homogenous grain diameter is generated. The incorporation of NCZFO generates irregular shape grain. The generation of irregular shape grain with the escalation of NCZFO amount is ascribed to the filling of pores and their segregation at the grain borders. The electric permittivity declines as NCZFO content escalates because of the effect of dilution whereas the electric permittivity enhances with Ts. Different models have been used to calculate the electric permittivity. The discrepancy in the midst of the theoretical and observed values of the electric permittivity is related to ion’s diffusion and interplay in the midst of two phases. Porosity correction of experimental electric permittivity is performed. A close coincidence in the midst of the porosity corrected electric permittivity and observed electric permittivity is achieved. Electrical conduction is caused by the small-polaron hopping. Impedance study suggested that the grains have less impact on overall electrical traits than grain borders. The magnetic permeability improves while the resonant frequency drops as NCZFO content escalates. The deterioration in resonant frequency is due to the increased domain wall motion. The magnetic permeability was calculated using different models and a comparison in the midst of experimental and calculated values is made. The difference in the midst of the theoretical and measured values of magnetic permeability is accounted to the interplay in the midst of two phases and ion diffusion. (1-y) [BCZTO] + (y) [NCZFe2-xO4-3x/2] (x = 0.0; 0.04; 0.08; 0.12, and y = 0.2; 0.5) FEMCCs were manufactured employing the solid state sintering technique and annealed for 5h at 1200 ℃. XRD and FTIR studies confirmed that the component phases existed simultaneously without any undesired phases. There are non-systematic variations in lattice constants, crystallite diameter, and cell dimensions as IDNS level escalates. SEM examination confirmed the development of polyhedral or irregular grains with insignificant agglomeration and porosity as IDNS escalates. Maxwell-Wagner’s interfacial polarization is responsible for the low-frequency electric permittivity dispersion. The ac electrical conductivity act in accordance with Jonscher's law and is controlled by the charge transfer in the midst of the adjacent localized sites and small-polaron hopping. The combined effects of strongly conducting grain and poorly conducting grain border responses, according to Nyquist plots, are thought to be the cause of electrical conduction phenomena. The magnetic permeability improves in x = 0.04, depreciates on increasing IDNS amount in y = 0.2, and then escalates on increasing IDNS amount in y = 0.5. The elastic interplay in the midst of the component phases, which is mediated by strain, results in an optimal magnetoelectric coefficient of 0.17 V cm-1Oe-1 in x = 0.0; y = 0.5 FEMCC. Finally, it is concluded that the achieved results make a significant contribution in designing and developing the next generation multifunctional devices in near future.