Synthesis of yttrium aluminium garnet by the gel entrapment technique using hexamine

A novel technique has been developed for the preparation of yttrium aluminium garnet (YAG), represented by the chemical formula Y3Al5O12, by achieving the homogeneous precipitation of the constituent metal hydroxides from the stoichiometric mixture of the metal nitrate solution by the addition of hexamethylene tetramine solution. Aluminium ions form a gel at pH 4, entrapping all the liquid, followed by the precipitation of yttrium ions at a higher pH. In spite of the sequential precipitation, the resultant mass is homogeneous because of the gel entrapment. Using this technique, single-phase YAG powder of high specific surface area (80 m(2) g(-1)) was obtained at 810 degrees C. Characterisation was done by thermogravimetry, differential thermal analysis, X-ray diffraction and scanning electron microscopy to ascertain the high quality of the product. The technique was subsequently used for the production of high-purity neodymium-doped YAG powder with excellent microhomogeneity on an increased batch size of 1 kg.