High Temperature Measurement of Complex Permittivity and Permeability of Fe₃O₄ Powders in the Frequency Range of 0.2 to 13.5 GHz

摘要

The real and imaginary parts of relative permittivity (ε_(r)′ and ε_(r)″) and permeability (μ_(r)′ and μ_(r)″) of Fe_(3)O_(4) powder were successfully measured over the temperature range of 25–575°C by means of the coaxial transmission line method in order to elucidate the heating behaviours of Fe_(3)O_(4) powder. The measurement frequency range is from 0.2 to 13.5 GHz. With respect to the temperature dependencies of the complex permittivity, the ε_(r)′ values show a peak around 450–500°C. The ε_(r)″ values monotonically increase with increasing temperature, in particular, showing abrupt increase above ca. 400°C. As for the complex permeability, the μ_(r)′ values decrease with an increase in temperature, and reach the same level as that of vacuum (μ_(r)′=1) at 575°C, i.e. , the maximum measurement temperature. The μ_(r)″ values increase with temperature until 500°C below 3.5 GHz although they monotonically decrease with an increase in temperature above 3.5 GHz.