抄録
The topotactic thermal-transformation of diaspore to corundum by dehydration was studied by thermal analyses, X-ray methods, BET, scanning electron microscopy and high temperature optical microscopy. Diaspore from Mitsuishi, Japan was used for this study.
The topotaxial relationship between the original diaspore and the developed corundum, first pointed out by Deflandre (1932), was confirmed. When diaspore transforms into corundum, (0001) twinning occurs. The ratio of twin individuals is 1:1. Striations, micropores and microcracks were observed in the heated diaspore and a pronounced increase of the surface area was proved.
When diaspore was heated at 500°C for 1 hour the O-H-O bond length changed from 2.62Å to 2.67Å. This suggests a widening of the openings of the channels linking the octahedral voids of diaspore.
