High Temperature Measurement of Complex Permittivity and Permeability of Fe_3O_4 Powders in the Frequency Range of 0.2 to 13.5 GHz

摘要

The real and imaginary parts of relative permittivity(ε_τ~' and ε_τ~") and permeability (μ_τ~' andμ_τ~") of Fe_3O_4 powder were successfully measured over the temperature range of 25-575℃ by means of the coaxial transmission line method in order to elucidate the heating behaviours of Fe_3O_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_τ~' values show a peak around 450-500℃. The _τ~" values monotonically increase with increasing temperature, in particular, showing abrupt increase above ca. 400℃. As for the complex permeability, the μ_τ~' values decrease with an increase in temperature, and reach the same level as that of vacuum (μ_τ~'= 1) at 575℃, i.e., the maximum measurement temperature. The ε_τ~' values increase with temperature until 500℃ below 3.5 GHz although they monotonically decrease with an increase in temperature above 3.5 GHz.