ИСТИНА

Under treatment of oxides or hydroxides of metals in supercritical water fluid occurs a solid-phase reorganization and ordering of oxides structure with formation of fine crystalline product that represent a powder of well-formed single crystals. The adding into reaction medium of dopant as salt or oxide leads to introduction into structure of forming crystals about half of dopant ions. Thermovaporous treatment (TVT) of aluminum hydroxide along with dopant at 400ºC and P(H2O) = 26 MPa results in formation of corundum (alpha-Al2O3) with intensive luminescence bands at 694 nm (Cr), 678 nm (Mn), 614 nm (Eu). The synthesis of gahnite (ZnAl2O4) doped by Cr or Eu results in occurrence of luminescence bands at 687 and 612 nm. The synthesized LaAlO3:Eu has intensive narrow luminescence bands at 591, 616 and 618 nm. The doping of yttrium - aluminum garnet by Cr (Y3Al5O12:Cr) results in appearance of luminescence centers of two types with bands at 688 and 694 nm. The formation of oxide structure proceeds in conditions of quasi-equilibrium with water vapor according to a solid-phase mechanism. The formation kinetics of doped corundum is described by the Erofeev equation for a case of ramified chain nucleation, and formation of the complicated oxide by this equation with constant nucleation rate. The formation of oxides in medium of water vapor and water is accompanied by appearance of oxygen vacancies and hydroxyl groups in structure. The annealing of obtained oxides at high temperatures results in removal of residual hydroxyl groups and change of a state of point defects of structure with rise of luminescence intensity.