The Synthesis And Properties Research Of Nano-structured LiNbO₃and KNbO₃

With the development of micro-/nano-fabrication technology, nano-materials such as nanoparticles, nanowires, nanotubes, and nanoneedle, have showed inviting application prospect in the new and high technology fields. They have many advantages in producing light emitting diode, integrated circuit, optical switch, light catalysis, and biological probes, therefore, have attracted much attention and research from all around the world.Lithium niobate and potassium niobate which have excellent piezoelectric, ferroelectric, dielectric, photorefractive and nonlinear optical properties, as well as high chemical stability and good biocompatibility are two kinds of typical alkali niobate materials. They have broad application prospects in many fields, such as optical fiber communication, lighting equipment, laser frequency conversion, and biomedical fields. However, the research on nano-structural lithium niobate and potassium niobate is still in its infancy without significant achievements. Therefore, it is really urgent and important to study on their synthesis and properties.In this thesis, KNbO3nanoneedles were synthesized using hydrothermal method with a polycrystalline Al2O3as substrate, KOH, Nb2O5, and H2O as reactants; LiNbO3nanoparticles were synthesized through molten salt method, with KNbO3nanowires which were synthesized by hydrothermal method and LiNO3powders in melting KCl; LiNbO3nanowires were also synthesized using a four steps’ molten salt method with Nb2O5, KCl, HNO3, and Li2CO3as reactants. It was proved that these three products were all pure and highly crystallized based on the characterization and analysis of their morphologies, phase compositions, and structures. The formation mechanisms of these three products were well analyzed. Finally, their second harmonic generation properties, cell toxicity, and biological imaging capability were further studied. It was proved that all the products were highly sensitive to frequency transformation, had stable luminous intensity without light bleaching or light flashing phenomenon. MTT test also showed their low biological toxicity. In biological imaging experiments, all of them showed a high luminous intensity and distinct imaging contrast avoiding interference of background. The synthesis and properties’study on nano-structural lithium niobate and potassium niobate in this thesis will provide a further guide for the development and application of micro-/nano alkali niobate materials, leading to an outstanding performance.