HIGH-VOLTAGE HIGH-RESOLUTION ELECTRON-MICROSCOPY ON THIN-FILMS OF MONODISPERSED PSEUDOCUBIC AND PEANUT-TYPE HEMATITE PARTICLES

In order to investigate internal structures of monodispersed hematite (alpha-Fe2O3) particles of pseudocubic and peanut-type shapes prepared by the gel-sol method (J. Colloid Interface Sci., 152 (1992), 587; Co lloids Surf. 70 (1992), 167), their thin sections were prepared by an ultra-microtome and studied by transmission electron microscopy. The s urfaces and arrangements of the individual small subcrystals as compon ents of the monodispersed particles were clearly observed on the atomi c scale by high-voltage high-resolution electron microscopy. This is d irect evidence of the polycrystallinity of these particles. Furthermor e, it was found that the subcrystals of the pseudocubic particles had a square shape bounded by sharp {01 (1) over bar 2} surfaces lining up with the same orientation, whereas those of the peanut-type particles had relatively round surfaces and the crystallographic orientations o f adjacent subcrystals slightly differed from each other.