INTERNAL STRUCTURE-ANALYSIS OF MONODISPERSED PSEUDOCUBIC HEMATITE PARTICLES BY ELECTRON-MICROSCOPY

Morphology and internal structure of monodispersed pseudocubic hematit e (alpha-Fe2O3) particles produced by the gel-sol method were investig ated in detail through high-resolution electron microscopy on their th in sections prepared with an ultramicrotome. It was confirmed that the c-axis of a particle corresponded to the longest diagonal axis of the particle. High-resolution electron micrographs of thin sections direc tly revealed the polycrystallinity of the particles and clearly showed the arrangement of the subcrystals and their crystallographic orienta tions. The subcrystals near the surface of a particle were of a rectan gular shape bound by the {<01(1)over bar 2>} planes, and their width w as about 12-16 mn with small variation of the length depending on the position in a particle. The subcrystals were radially developed from t he center of a particle in all directions, but most preferentially in the longest diagonal axis of a particle. Besides, it was found from ED X analysis that the adsorbed Cl- ions as a shape controller were incor porated into the pseudocubic hematite particles during their growth. ( C) 1996 Academic Press, Inc.