The Electrical And Optical Properties Studied By Density Functional Theory And The Growth Of Potassium Doped Lithium Niobate

First-principle theory was used to analysis the optical and electric properties ofthe potassium doped lithium niobate single crystal. The structural model of thesingle crystal had beed established. The crystal structure, energy, electronicproperties, optical properties and phonon spectra were calculated after geometryoptimization. The doping changed the lattice parameters of the cystall cell andenlarged the volume. The analysis of the band structure showed these cystals in thispaper are all p-type semiconductoers and the band bap were narrowed with thepotassium concentration increasing. It is verified niobate ionic would instead thelithium sites in the crystal. The reflection spectra, refraction spectra, absorptionspectra, dielectric spectra, conductivity and loss function spectra of the potassiumdoped lithium niobate had been discussed and these spectra showed better opticalproperties when potassium as a dopant in lithium niobate. The calculation resultsshowed the ferroelectricity of lithium niobate.A series of lithium niobate single crystals doped with x mol%potassium (x=0,3,6,9,12mol%) were successfully grown by Czochralski method. The crystalswere characterized by powder X-ray diffraction, UV-vis-infrared absorptionspectrum, ferroelectric property test and differential thermal analysis test.X-ray powder diffraction analysis showed that the changes of the latticeparameters in potassium-doped lithium niobate, and the increase of the cell volume.UV-visible absorption spectra show the red shift of the absorption edges indicatedthe doping narrowed the optical band in the crystals. With the increasing ofpotassium concentration, hysteresis loop areas increased significantly, indicatingthat the crystal spontaneous polarization increased, and the increasing offerroelectricity in potassium-doped lithium niobate. Differential thermal analysisshowed that higher melting point of the potassium doped crystals. The experimentalresults had consistented with the theoretical analysis well. The enhancement of the ferroelectricity indicated the more distort lattice in potassium-doped lithium niobate,and will predict more nonlinear optical performance in the crystals.