Microstructural and electromagnetic study of low temperature fired nano crystalline MgCuZn ferrite with Bi2O3 addition

The present study investigates electromagnetic properties, as well as microstructural and thermal stability, of low temperature fired MgCuZn ferrite with the addition of various amounts of Bi2O3. To achieve better performance at low sintering temperature, ceramic specimens were fabricated using nano-sized precursor powders through the nitrate-citrate auto-combustion method. X-ray diffraction study shows the formation of single phase spinel structure without any impurity phases. Compared with the additive-free sample, the addition of Bi2O3 increases the density of all specimens. Scanning electron microscopy micrographs of samples indicate that Bi2O3 content significantly affects densification through grain growth promotion. Excessive amounts of Bi2O3, however, lead to abnormal grain growth. Moreover, the sample with 0.25 wt% Bi2O3 shows the highest density and grain shape uniformity as well as the lowest porosity. Dynamic magnetic properties were studied in a frequency range of 1-90 MHz, using an impedance analyzer. Results reveal that the sample with a low amount of additive (0.25 wt%) has the highest saturation magnetization, initial permeability (at 1 MHz), and quality factor, whereas it's Curie temperature slightly decreases. With the further increase of Bi2O3 content, however, the initial permeability and saturation magnetization of samples deteriorate gradually.