Synthesis of yttrium aluminum garnet from a mixed-metal citrate precursor

Abstract

Yttrium aluminum garnet (YAG, Y3Al5O12) was synthesized using a polymeric precursor derived from a mixed-metal citric acid/ethylene glycol/ethanol solution. YAG was found to crystallize directly from an amorphous precursor beginning at temperatures as low as 600°C within 1 h in air. The polymer resin concentration was found to have an effect on the temperature of crystallization initiation. However, all precursors produced a well-crystallized YAG powder within 1 h at 800°C in air. Formation of phase-pure YAG in an argon atmosphere did not occur until heating for 1 h at 1000°C. An optimum cation-to-resin ratio to maximize reactivity provides a polymeric network to ensure a homogeneous dispersion of cations, yet minimizes cation diffusion distances within the char by limiting excess free carbon after polymer pyrolysis.