Precipitation and calcination processes for yttrium aluminum garnet precursors synthesized by the urea method

Yttrium aluminum garnet (YAG) precursors for transparent ceramics were synt hesized by the urea method under various [urea]/[metal ions] ([U]/[M]) cond itions. Monophase YAG was obtained from solutions with a high [U]/[IM] rati o after calcination at a temperature of 1200 degrees C. The condition of th e precipitates seemed to indicate that the yttrium compounds had precipitat ed onto the aluminum compounds. The surface morphology and size of the part icles were controlled by the [U]/[M] ratio. The different reaction sequence s of YAG crystallization for low- and high-ratio samples were dependent on morphology, size, and the quantity of chemical species that was precipitate d as carbonate and/or sulfate compounds.