Synthesis Technology Of Lithium Niobate Powders Via Wet Chemical Routes

Lithium niobate is well known as an excellent functional material due to its ferroelectric,piezoelectric, electro-optic, acousto-optical, pyroelectric, photorefractive, and large nonlinearoptical coefficients. Recently, lithium niobate powders have also been proven to exhibit highphotocatalytic activity without a trace of photocatalytic deactivation. With the development offunctional devices, the study of lithium niobate powders has been one of the hot topics inmany countries.This thesis mainly focuses on the synthesis of lithium niobate powders by two wetchemical methods according to choosing the proper reactants.An ethylene glycol (EG)/water system has been designed to synthesize lithium niobatepowders by a mild, one-step method. A morphology transformation from initial nuclei toflowerlike structures, and then to hollow spheres is conformed by the time-dependentexperiment. The formation mechanism of the hollow spheres is presumed by a careful controlof the experiment conditions and the absorption edge of the products in UV/vis diffusereflectance spectra can be effectively tuned by the current morphology control strategies. Thiswork will extend the potential applications of lithium niobate powders.Further more, hydrogen peroxide and aqueous of ammonia which are introduced in thesolvent, can react with niobium acid. The obtained precursor can react with lithium hydroxideto form lithium niobate at a mild condition. The products can be characterized by X-raypowder diffraction and FT-IR spectra. The transformation process of morphology isexamined by Scanning Electron Microscope(SEM).This thesis introduces two mild routes to synthesize lithium niobate powders, whichavoid the disadvantages of high temperature solid-state route and attain the effectivemorphology control of lithium niobate powders. Moreover, the flower-like and hollow sphereparticles are synthesized for the first time and their absorption edge in UV/vis diffusereflectance spectra can be effectively tuned by the current morphology control strategies.These mild solvothermal methods may be extended to the synthesis of other kinds of nano- ormicrostructures with unique morphologies.