Two series of magnesium–manganese ferrites, viz. Mg0.9Mn0.1InxFe2 − xO4 and Mg0.9Mn0.1CryFe2−yO4 have been prepared by the conventional ceramic process. The effects of In3+ and Cr3+ ions on the dc resistivity, dielectric constant and dielectric loss factor are presented in this paper. The resistivity increases with increasing concentrations of In3+ and Cr3+ ions. The observed variations in resistivity have been explained by Verwey's hopping mechanism. The activation energy, deduced from the temperature variation of resistivity, was found to increase with increasing concentrations of In3+ and Cr3+ ions. The room temperature dielectric constant at 100 kHz decreases with successive addition of trivalent ions in both the series. The observed variation in dielectric constant has been explained on the basis of space charge polarization. The dielectric loss tangent (tanδ) values measured at 100 kHz and 13 MHz are found to be very low for the samples with a higher concentration. The low values of the loss factor even at a high frequency indicate that the prepared materials may have great potential for use in microwave devices.
Dielectric properties such as DC resistivity (ρ), dielectric constant (ε) and dielectric loss factor ( tan δ) have been measured for Mg 0.9 Mn 0.1 In x Fe 2-x O 4 and Mg 0.9 Mn 0.1 Cr y Fe 2-y O 4 at room temperature. The composition dependence of ρ, ε and tan δ and the frequency dependence of ε and tan δ are presented in this paper. The resistivity increases while the dielectric constant decreases with increasing concentrations of indium and chromium ions. The dielectric loss factor at 100 kHz increases with composition for the samples 0.1 ≤ x ≤ 0.9 and 0.1 ≤ y ≤ 0.7. The dielectric constant for a given sample decreases with increasing frequency showing the normal dielectric behavior. The values of dielectric loss factor have been found to increase with frequency for the samples corresponding to x or y = 0.1 to 0.5; while other samples showed abnormal dielectric behavior. The observed variations in ρ are explained by Verwey's hopping mechanism while the variations in ε and tan δ with composition and frequency are explained by space charge polarization using Koop's theory. Higher values of DC resistivity and low dielectric losses suggest that the prepared materials have great potential for microwave and high-frequency applications.
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