Microwave permittivity, permeability, and absorption capability of ferric oxide

Abstract

The permittivity and permeability measurements of ferric oxide (Fe 2O 3) were carried out over a broad temperature range from 24°C to above 1 000deg;C at 915 and 2 450 MHz. The real part and imaginary part of complex relative permittivity (ε r′ and ε r″) of ferric oxide slightly increase with temperature below 450deg;C, above which ε r′ increases significantly while ε r″ presents a broad dielectric loss peak between 450 and 1 000deg;C. Contrary to ε r′ and ε r″, the real part and imaginary part of complex relative permeability (μ r′ and μ r″) remain relatively invariable (1 and 0, respectively) until 700deg;C. The μ r′ values subsequently exhibit a decreasing tendency due to the increased electrical conductivity at higher temperatures while the μ r″ values stay negligible as temperature increases. The results demonstrate that the dielectric loss is the primary factor contributing to microwave absorption of Fe 2O 3. The calculation of microwave penetration depth shows that Fe2O3 undergoes a transition from a microwave transparent material to a good microwave absorber with increasing temperature. © 2012 ISIJ.