Transparent lutetium aluminum garnet sintered from carbonate coprecipitated powders

Pure phase lutetium aluminum garnet (LuAG) powders have been obtained by coprecipitation from a mixed solution of aluminum and lutetium nitrate using ammonium hydrogen carbonate (AHC) as precipitant, followed by calcination of the dried precipitates at 1000°C. The use of AHC as the precipitator and reverse-strike precipitation method can effectively avoid the formation of gelatinous hydrate precursor at high CO₃^2-- to -OH ^- mole ratio in the solution. This is pivotal for the control of chemical homogeneity within the particles as well as the agglomeration and size of the particles. X-ray diffraction (XRD) and TEM analysis showed that the synthesized powder was single-phase LuAG, with weakly-agglomerated fine spherical grains (20 nm average) and a relatively narrow grain size distribution. The powders could be easily sintered into transparent LuAG ceramic in H₂ atmosphere at 1850°C.