Structural transformations in the Al2O3-H2O system

The paramagnetic probe method was used to study the hydrargillite-boehmite- corundum structural transformations during quasi-equilibrium dehydroxylatio n in the atmosphere of water vapor at 200-400 degrees C. An increase in the temperature of boehmite formation from 200 to 350 degrees C causes perfect ion of its structure followed by the transition to corundum at 400 degrees C and P-H2O = 26.0 MPa. Ordering of the boehmite structure is accompanied b y a decrease in the volume of the unit cell. The formation of the corundum lattice is accompanied by initial disordering of the oxide phase with reten tion of specific defects in the produced corundum structure. The defects ar e removed by high-temperature annealing.