Synthesis of Rare-Earth Gallium Garnets by the Glycothermal Method

Single-phase rare-earth gallium garnets were obtained by the reaction of stoichiometric mixtures of gallium acetylacetonate and rare-earth (Nd-Lu) acetates in 1,4-butanediol at 300°C (glycothermal reaction). Particles of gadolinium gallium garnet (GGG) and other gallium garnets with rare-earth elements larger than Gd were spherical with diameters of 0.5-2 μm, while particles of garnets with smaller rare-earth ions (Tb-Lu and Y) were much smaller (100-300 nm) with particle size distributed in a quite narrow range. TEM observation revealed that each particle was essentially a single crystal grown from one nucleus, but that defects frequently occurred during the crystal growth. Cerium and praseodymium gallium garnets were also formed when the reaction was carried out in the presence of GGG seed crystals. Hydrothermal reactions of the same starting materials under identical conditions yielded mixtures of gamma-Ga₂O₃ and the garnet phase.