Crystallographic Study for unknown phase of alumina on a dehydration of gibbsite.

Abstract

A single crystal of gibbsite (Al(OH)₃)was studied by in-situ monochromatic Laue method in order to characterize new unknown phase of alumina (Al₂O₃), X-phase, on dehydration process from gibbsite into corundum (a-Al₂O₃). Experiments were performed at BL4B-1, KEK, using X-ray diffraction equipment for micro-size crystal with Imaging Plate and a heating stage. A specimen of gibbsite crystal was put on the heating stage, heated onto 600 C, and exposed into X- rays monochromatized in 1.0A by Si (111) double crystal monochromator and collimated into 100 micrometer. The measurement time and interval of heating temperature were synchronized. Diffraction from X phase of alumina was observed on a Laue photograph around 200 C area, and there reflections were broadened, that means the size of crystallite of X- phase is very small as well as gamma-alumina.