Sol-Gel Synthesis and Optical Studies of Rare Earth and Transition Metal Ions Doped Nanocrystalline Aluminum and Yttrium Oxides

The paper reviews the studies of sol-gel produced nanocrystalline -Al₂O₃ and cubic Y₂O₃ doped with RE³⁺ and TM³⁺ ions. The effects of spatial confinement (on nanometer scale) in optical properties of sol-gel produced insulating nanocrystalline oxide materials doped with rare earth and transition metal ions are discussed. The experimental studies showed that in insulators these effects are mostly connected with the changes in the vibrational spectrum and the increased role of the surface in nanocrystals. The transformations between the crystalline forms of Al₂O₃ and the properties of doped corundum ceramics are studied. The methods of sol-gel synthesis of highly dispersed nanocrystalline -Al₂O₃ and cubic Y₂O₃ doped with RE³⁺ and TM³⁺ ions in wide range of concentrations are described. It is shown that optical techniques are useful for characterization of sol-gel produced materials.