ИСТИНА

In this report the method of a producing of fine crystalline Yttrium Aluminum Garnet doped with Cerium (YAG:Ce3+) in supercritical water fluid (SCWF) are represented. This way allows obtaining high-pure fine crystalline materials. The YAG:Ce3+ was synthesized by way thermotreatment of mechanical stoichiometric mixture from yttrium oxide and aluminum hydroxide in water vapor in two stages: at 280 °C (PH2O=6.3 MPa) and then at 400 °C (PH2O=22 MPa). A cerium nitrate was added to starting mixture. The concentration of cerium ions in reaction medium was changed in an interval 0.012 - 0.706 % concerning a final product. The products of a synthesis were investigated by methods of X-ray diffractometry, FTIR-spectroscopy, electron microscopy and diffuse reflectance. It was found that the formation of crystals of YAG:Ce3+ is preceded by an induction period, which is the time required for formation of intermediates (yttrium hydroxide and oxyhydroxide crystals). The induction period can be changed by the addition of dopant into reaction medium. During this period the aluminum component is amorphous. During the induction period the diffusion of aluminum ions and cerium in the structure of yttrium hydroxide is begun and at the end of the induction period the formation of the garnet structure occurs. The role of the water fluid consists in the increase of the mobility of reagents lattice and in the facilitation of the components diffusion to form the final product – YAG:Ce3+. The crystals size of as-prepared YAG:Ce3+ was in the 0.5 – 3.0 µm range. The crystals have rhombododecahedral habitus. These samples showed the intensive yellow photoluminescence at 530 nm.