Microstructure analysis of Fe3O4 heated by microwaves in a TE10 mode cavity: surface and volume characterization.

Detailed observations of the single mode H-field heated magnetite was conducted. The heated magnetite contains a shiny area, which exists in the width of 5 mm and thickness in 1 mm. The observation of the area reveals wavy surface patterns. The microstructures of the shiny area consists of an undefined phase and a magnetite phase which fills the space among the undefined phases. The XRD pattern from the shiny area is different from that of the random magnetite crystals, which is caused by the magnetite grains having almost same orientation in large area. There are banded areas surrounding the undefined phase of several microns in thickness, in which the existence of nano-sized crystals is indicated by means of EBSD and TEM.