Influence of sintering additives and substitution on magnetic and dielectric properties of Co2Z hexaferrite

Abstract

Co2Z ferrite (Ba3Co2Fe24O41) has gained considerable attention in high-frequency microwave devices. The ferromagnetic resonance of 1.3 GHz and low losses at microwavefrequencies makes it a suitable material for miniaturized mobile and wireless LAN communication. Co2Z ferrite also exhibits magneto-electric (ME) coupling for application in nonvolatile memories, spintronics, and microwave devices. The magnetic and dielectric properties of Z-type ferrites were studied with different cations substitutions for Ba2+, Co2+, and Fe3+. The dielectric loss of the material is associated with the microstructural characteristics namely grain size, shape, and the concentration of the porosity. The higher temperature sintering improves the dielectric losses due to the grain growth and the reduction of the Fe3+ into Fe2+. The magnetic and dielectric losses can be minimized with the varying sintering process conditions, time, and temperature. Some sintering additives are also used to modify the magnetic, dielectric, and microstructural features. Additives facilitate to form liquid phase along the grain boundary and lead to refining the grains. The small grain size significantly decreases the dielectric losses. Recently the dielectric properties and impedance spectroscopy of Z-type hexaferrite have been investigated in GHz. At higher frequencies, the contribution of grain boundary is very difficult to achieve. Generally, the electrical response of the grain and grain boundaries are obtained in the frequency range of 10 kHz to 1 MHz. In this dissertation, Z-type hexaferrite (Ba3Co2Fe24O41) is synthesized and the effect of the various sintering additives (SiO2, MgO, Al2O3 & Bi2O3) and cation substitutions (La3+, Ca2+for Ba2+ and Al3+ for Fe3+) on structural, magnetic and dielectric properties were investigated.