Structure of hercynite prepared with existence of metal Fe

In this work, raw materials analytically pure Al2O3 and analytically pure Fe2O3 were mixed in FeO: Al2O3 molar ratio of 1 : 1 and pressed into specimens. The specimens were embedded in analytically pure metal Fe powders and fired slowly to 1650 degrees C in air atmosphere, and then soaked at 1650 degrees C for 5 hrs. The fired specimens were investigated by XRD, SEM, and EDS. The results show that the specimen synthesized at high temperatures in melting Fe is composed of hercynite and wustite (FenO (n <= 1)); FenO disperses in hercynite; hercynite crystals develop well and are mostly perfect octahedron with grain size around 50 mu m. The hercynite has Fe/Al ratio smaller than 1/2, which is non-stoichimetric. With the existence of melting Fe, although the raw materials are theoretically batched according to FeO center dot Al2O3, FenO is still excess, so the hercynite obtained is Al-rich.