Microwave Absorption Characteristics of Conventionally Heated Nonstoichiometric Ferrous Oxide

The temperature dependence of the microwave absorption of conventionally heated nonstoichiometric ferrous oxide (Fe(0.925)O) was characterized via the cavity perturbation technique between 294 K and 1373 K (21 A degrees C and 1100 A degrees C). The complex relative permittivity and permeability of the heated Fe(0.925)O sample slightly change with temperature from 294 K to 473 K (21 A degrees C to 200 A degrees C). The dramatic variations of permittivity and permeability of the sample from 473 K to 823 K (200 A degrees C to 550 A degrees C) are partially attributed to the formation of magnetite (Fe(3)O(4)) and metal iron (Fe) from the thermal decomposition of Fe(0.925)O, as confirmed by the high-temperature X-ray diffraction (HT-XRD). At higher temperatures up to 1373 K (1100 A degrees C), it is found that Fe(0.925)O regenerates and remains as a stable phase with high permittivity. Since the permittivity dominates the microwave absorption of Fe(0.925)O above 823 K (550 A degrees C), resulting in shallow microwave penetration depth (similar to 0.11 and similar to 0.015 m at 915 and 2450 MHz, respectively), the regenerated nonstoichiometric ferrous oxide exhibits useful microwave absorption capability in the temperature range of 823 K to1373 K (550 A degrees C to 1100 A degrees C).