不同切型掺铈Ce:BaTiO3晶体SPS -SPPC特性及机理研究

研究了0°切和45°切Ce:BaTiO3晶体的受激光折变散射自泵浦相位共轭(SPS-SPPC)特性,获得的最大共轭光反射率分别为67 %和80 %.比较了两种样品内部光路形成的特点,实验结果表明,45°切样品不仅具有更高的反射率,而且入射角在较大范围内都能获得较高的共轭光反射率.对此作了理论分析.     

The formation of titania polymorphs under hydrothermal condition

The formation process of crystal polymorphs of titania under hydrothermal condition is studied. According to the experimental results and theoretic analysis, the formation process of crystal polymorphs can be described as a unit process. It includes the formation of growth units, the formation of nuclei through the polymerization of growth unit, and the growth of crystallites. The influence of the environmental phase and growth conditions on the formation of polymorphs is reflected in the changes of the structures of growth units. For example, when changing the pH of the reaction medium, the structure of growth unit with the highest stable energy in the hydrothermal system changes. Then different titania polymorphs can be prepared. The absorption, movement, crystallization or desorption of the growth unit are related to crystalline structure. On the other hand, the formation of crystal inner defects is related to the disturbance of the crystallizing process.     

Formation of zirconia polymorphs under hydrothermal conditions

Using zirconium oxychloride solution as precursor, monoclinic zirconia crystallites with narrow distribution of nanosize were obtained in the hydrothermal reaction. However, when the reaction was in weak acidic medium or base medium, whether directly using the colloidal precipitate prepared from zirconium salt solutions with base solution as precursor added, or using the precipitate after filtrating, washing and drying treatments as precursor, the product of the hydro-thermal reaction was the mixture of both monoclinic and tetragonal polymorphs. As the pH of the medium rises, the content of tetragonal phase in the product, the morphologies and size of the crystallites all change. There are three types of formation mechanisms under hydrothermal condition, which can be called as saturation-precipitation mechanism in homogeneous solution, dissolution-crystallization mechanism and in-situ crystallization mechanism, respectively. The formation mechanism of crystallites varies with different hydrothermal condi