ИСТИНА

Kinetics and mechanism of alpha-Al2O3 (corundum) formation from Al(OH)3 (hydrargillite) in supercritical water fluid at the presence of manganese ions was investigated. In these conditions of the hydrargillite powder transformation in small single crystals of corundum doped with manganese was obtained. It is found that the corundum synthesized in medium of supercritical water with the Mn2+ ion or MnO4– anion contain one-type composite defects containing ions Mn4+ discovered by photoluminescence method. Mn3+ discovered by diffuse reflection spectroscopy method and Mn2+ (observed by EPR method) alongside with hydroxyl groups and oxygen vacancies were formed the complex centre, consisting from exchange-bonded manganese ions and charged oxygen vacancy: Mn4+-VO-Mn2+. The appearance of manganese ions with a different charge in corundum structure is determined by oxidation-reduction properties of supercritical water fluid.