Synergistic Effect of Zirconia and Impurities on the Properties of Mn-Zn Ferrites Synthesized by Mixed Oxide and Auto Combustion Routes

Abstract

Two methods namely, conventional mixed oxide and sol gel auto combustion have been adopted to synthesize Mn-Zn Ferrite powder. In sol gel process, nanosized Mn- Zn Ferrite powder was obtained by starting auto combustion reaction in gel containing metal precursors. In each method, electromagnetic properties (saturation magnetization, Curie temperature, magnetic impedance and loss tangent) have been measured after sintering the green compacts (pellets and toroids). The results revealed that Mn-Zn Ferrite synthesized by sol gel auto combustion process had superior electromagnetic properties than conventional mixed oxide method because of possessing single phase and refined microstructure. Apart from the effect of synthesis routes, the role of zirconia (ZrO 2 ) additive (0.2, 0.4 and 0.6 wt%) along with/without impurities i.e. calcia (CaO) & silica (SiO 2 ) on the electrical and magnetic properties of Mn-Zn Ferrite have also been studied. In conventional mixed oxide method, it has been observed that Z2-series (0.2 wt% ZrO 2 along with/without CaO & SiO 2 ) have better electromagnetic properties than pure and other synthesized compositions (Z4-series and Z6-series). It was mainly due to the fine control of grain growth process during sintering. The same series (Z2-series) have also been synthesized by sol gel auto combustion process. Further improvement in magnetic impedance was observed due to the simultaneous effect of zirconia along with impurities and adopted synthesis route. Among all the synthesized compositions, Mn-Zn Ferrite containing 0.2 wt% ZrO 2 & 0.04 wt% CaO synthesized by sol gel auto combustion process possessed optimum properties at high frequency ( > 500 KHz). The presence of smaller grains having faceted morphology and formation of insulating phase along grain boundaries enabled this composition to operate at high frequency band (i.e. 3 MHz to 20 MHz). The operational frequency band of this composition was further broadened (i.e. 100 KHz to 18 MHz) by improving the sintering conditions. Furthermore, light weight and compact size (washer type) toroid core of this selected composition was prepared and tested in lab scale fabricated linear pulse amplifier circuit. The results showed that synthesized core was able to transmit even weak input signals (50 mV) without any loss. It was good achievement regarding the miniaturization of Mn-Zn Ferrite core transformers to meet the demand of modern switch mode power supply units. Beside this bulk study, highly textured Mn-Zn Ferrite films were also developed on glass substrate by using the target prepared by sol gel auto combustion process. Pulse laser deposition technique has been employed to deposit these films under controlled conditions. Results showed that the strain induced during the deposition process was responsible to attain texture in fabricated films. Because of possessing magnificent magnetic properties, fabricated film had a potential to utilize in memory and spintronic devices.