Glycothermal synthesis of rare earth iron garnets

The reactions of rare earth (RE) acetates with iron acetylacetonate in 1,4-butanediol at 300 degrees C (glycothermal reaction) yielded two novel phases depending on the ionic size of the RE element: one was obtained for Er-Lu and the other for Tb and Dy. The former phase was hexagonal REFeO3, while the latter phase has not been identified. The reaction of Y or Ho acetate yielded the mixture of these two phases. When the reactions were carried out in the presence of seed crystals of yttrium aluminum garnet (Y3Al5O12) these phases were not formed but RE iron garnet (RE3Fe5O12) grew on the seed, which suggests that spontaneous nucleation of RE iron garnet does not occur, but crystal growth proceeds easily under the glycothermal conditions. Hydrothermal reaction of the same starting materials yielded a mixture of Fe2O3 and an amorphous RE phase.