MICROSTRUCTURAL OPTIMIZATION OF LOW-TEMPERATURE-FIRED NI-ZN-CU FERRITES USING CALCINATION

The purpose of this work was to examine the effect of low-temperature sintering on the microstructural optimization of Ni-Zn-Cu ferrites. Th is behavior was evaluated with respect to calcination temperature. The amount of unreacted hematite produced during calcination was quantita tively analyzed using a new calibration curve obtained using X-ray pow der diffractometry. The formation of a spinel phase was initiated abov e 550 degrees C, and completed above 850 degrees C. The microstructura l optimization. of Ni-Zn-Cu ferrite samples was achieved using powder calcined at 750 degrees C, and these specimens showed a maximum permea bility of 700. A variation in microstructure with the change of the ca lcination temperature is ascribed as the cause of this optimization. T wo mechanisms for the optimization are also suggested. One is the form ation of hard agglomerates at high calcination temperatures and the se cond is the inhibition of grain growth due to the residual hematite in powders calcined at low temperatures. Microstructural optimization wa s achieved through a trade-off between these two mechanisms.