Effect of Ta 2 O 5 addition on the electrical and magnetic properties of nanocrystalline MgCuZn ferrites
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Ta2O5 added MgCuZn ferrites are prepared by the microwave-hydrothermal (M-H) processing. The nanocrystalline ferrites are sintered to a temperature of 900 °C using conventional sintering (CS) and microwave sintering (MW) methods. The effect of Ta2O5 addition on the microstructure, d.c. resistivity, and Curie temperature of the ferrites has been studied. By the addition of Ta2O5 to MgCuZn ferrites, resistivity decreases without grain growth. The complex permittivity and complex permeability of the prepared samples were measured in the frequency range from 10 kHz to 1.8 GHz. The value of e9 and tan d for all the samples decreases from 10 to 100 kHz and almost remains constant up to 300 MHz and increases further by increasing the frequency up to 1 GHz. The l* spectra are analyzed into two magnetization processes with a focus on the grain size of the ferrite samples. The present ferrites exhibited high values of permeability (.1000) in the frequency range of 10 kHz to 50 MHz. Then the values of permeability are found to decrease with an increase in frequency up to 180 MHz and finally, frequency dispersion occurred at 200 MHz.
I. INTRODUCTION
II. EXPERIMENTAL METHOD
MgCuZn ferrite is one of the important magnetic materials for many high frequency applications. This is because of its better properties at high frequencies such as high resistivity, high Curie temperature, environmental stability, low cost, and lower densification temperature than that of NiCuZn ferrites.1–3 In high frequency applications for Mg-based polycrystalline ferrites, porosity and resistivity are the main problems. These problems can be solved by the addition of additives. The proper selection of additives will also promote low-temperature sintering. The most commonly used additives are the low melting compounds such as CaO, Na2O, ZrO2, PbO, Ta2O5, V2O5 etc.4–6 In the present investigation, the additive chosen is Ta2O5. Ta2O5 has been studied intensively as capacitor materials due to its high dielectric constant and a high degree of compatibility with microelectronics manufacturing. It is considered as a promising dielectric material for the next generation of high density dynamic random access memories (DRAMs). 7–10 It is also observed that the addition of Ta2 O5 gives the fine grained microstructure. 11 Keeping these points in view, we have undertaken a study of the effect of Ta2O5 on electrical, dielectric, and magnetic properties of MgCuZn ferrites.
Pure (99.99%) chemicals of magnesium nitrate [Mg(NO3)26H2O], copper nitrate [Cu(NO3)23H2O], zinc nitrate [Zn(NO3)26H2O], iron nitrate [Fe(NO3)29H2O], and tantalum (V) ethylate (C10H25O5Ta) were dissolved in 50 mL of deionized water. The molar ratio of powders was adjusted to obtain composition Mg0.2Cu0.3Zn0.5Fe2O4. The nonmagnetic ions of Ta2O5 are added separately in the range of 0.2, 0.4, and 0.6 wt%. An aqueous NaOH solution was added to the prepared solution until the desired pH (;9.12) value was obtained. The mixture was then treated with Teflon-lined vessel using a microwave digestion syst
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