The Content Analysis And Dissolution Of Lithium Niobate Based On Chemical Methods

Lithium niobate is a typical non-stoichiometric crystal. The indirect opticalmeasurements are usually used for component measurement because of the chemicalbonds of lithium niobate between atoms structure are stable and not prone to chemicalreactions.Component measurement methods commonly used for, very difficult, mainlybecause This article is to decompose lithium niobate crystal by direct liquid reagent orsolid flux, so the chemical analysis methods could be directly utilized formeasurement of lithium niobate content.This work mainly contains the following parts:1. A series of characteristic methods for the crystal composition changes arediscussed and analyzed, such as the line width of Raman spectra of the lithiumniobate crystal, the Curie temperature, refractive index, phase matching angle andphase matching temperature, the crystal density and unit cell parameters, andphotorefractive properties.2．In addition to know more about the optical measurement methods of crystalcomposition, we did further research about the chemical analysis of a variety of waysand comparison of their advantages and disadvantages. Further more, the specific testmethod for analysis of lithium niobate components was selected, i.e. inductivelycoupled plasma emission spectrometry.3. The experimental research of the chemical dissolution of lithium niobate wasfinished. Four solvents of hydrofluoric acid, potassium hydrogen sulfate, lithiummetaborate and sodium metaborate were used to dissolve the lithium niobate crystal.First, we verified the feasibility of hydrofluoric acid for lithium niobatedissolution. During the analysis of the dissolution results, we find the lithium elementrelative error is3.7%, while that of niobium is10.35%. After that, the solubility oflithium niobate in hydrofluoric acid, which is (10.3~14.4) mg/ml, is derived by aseries of experiments. However, the strong corrosive of hydrofluoric acid, longexperimental period and complicated procedure make this method not ideal.Then we used a mixture of potassium hydrogen sulfate and lithium niobate,which was melted by heating by a alcohol lamp. We obtain that the solubility of lithium niobate crystals in potassium hydrogen sulfate is5.93mg/g. Nevertheless,this way is not easy to get a clear and transparent solution, and the solubility is lowerrelatively.Further more, we used borate fusion method. Though borate fusion demandshigher purity and the melting temperature of the flux, after enough experiments, wefinally found a molten lithium niobate lithium borate flux, Lithium metaborate. It hasstrong dissolve ability, and the melt can turn to the clear and transparent solution.However, due to the flux contains lithium element and the lithium element willevaporate at the high temperature,1050°C, the test results from the experiment andanticipated results does not fit quite well. Nevertheless, we still get the solubility oflithium niobate in lithium borate flux,(97.7~106.3) mg/g.Finally, we chose the flux of sodium borate as the more appropriate flux formelting lithium niobate. The reaction temperature of sodium metaborate is low, whichis about900°C. The solubility of lithium niobate is (75.3to80.0) mg/g, which isslightly lower than that in lithium borate. After the preparation of clear andtransparent solution, it was compared with the same ICP-AES test results, which isrelatively accurate. The result shows that the relative error of Li and Nb element are4.5%and5.5%, respectively. To sum that, we find a more feasible way to dissolve thelithium niobate crystal for content analysis.