Effect of firing temperature on the electromagnetic properties of electronic transformer cores developed by using nanosized Mn-Zn ferrite powders

Abstract

Current investigation deals with the effect of grain growth process as a function of sintering temperature on the electromagnetic properties (initial permeability, impedance, and gain) of Mn-Zn ferrite (MZF) cores (toroids). By employing auto combustion process, nanosized [(20 ± 5) nm] MZF powders were synthesized and toroid shape cores were obtained after subsequent calcination and firing (sintering) process. It was observed that the submicron structure (0.5 μm) achieved in the ferrite core sintered at 1,000 °C was gradually transformed into micron size grains by increasing the firing temperature i.e., 1,100, 1,200 and 1,350 °C. The results reveal that MZF core sintered at low temperature (1,000 °C) showed high impedance, low initial permeability and narrow working frequency range i.e., 3-15 MHz. However the improvement in initial permeability sintered density and operational frequency range (100 kHz-17 MHz) was observed at high temperature (1,350 °C) firing in the inert environment. This synthesized MZF core is more suitable for miniaturized switch mode power supply applications.