The influence of second phase precipitation on SiO2/GeO2doped Ni-Zn Ferrite properties

SiO
2
and GeO
2
have been found to have limited solubility in the Ni-Zn ferrite. SiO
2
having negligible solubility is seen to segregate as a dispersed phase, which reduces grain boundary mobility during sintering. Unreacted GeO
2
(m.p. ≃ 1100°C), on the other hand, forms a free flowing liquid phase, which wets the grain and promotes faster grain growth during sintering. The initial permeability decreases significantly with increasing GeO
2
additions. The bulk conductivity σ
dc
of the samples containing higher concentrations of these dopants shows an anamolous temperature dependence which is typical to the Schottky thermoionic emission. Such phenomena are discussed in terms of the second phase precipitation. The domain wall energy γ is also seen to increase significantly at higher dopant concentrations reflecting an increase in the internal stresses, caused primarily by these precipitates.