EFFECT OF PARTIAL SUBSTITUTION OF GE-4+ FOR ZN-2+ ON THE MICROSTRUCTURE AND TEMPERATURE STABILITY OF MN-ZN FERRITES

The effects of substitution of GeO2 for ZnO on the microstructure and magnetic properties of Mn-Zn ferrite have been studied. Results suggest that, to a very limited extent, by the substitution of Ge and a proper choice of sintering condition, good temperature coefficients can be obtained in a temperature range from 20 to 80°C. Experimental results show that the substitution of GeO2 promotes discontinuous grain growth, and the lattice parameter is slowly reduced due to the substitution of from 0.5 to 2.0 mol % GeO2 for ZnO. The temperature coefficient is extremely process sensitive. For appropriate Ge substitution (0.5%), optimum initial permeability and the temperature coefficient are dependent on the sintering conditions. Samples with 0.5 mol % GeO2 sintered at 1290°C using a rapid heating rate and short-time sintering yielded the best temperature coefficient of 0.1×10-6°C-1 over the range 20-80°C.