Designs,Syntheses And Properties Of Novel Mixed Ion Metal Iodates

Nonlinear optical（NLO）materials have attracted great attention because of their important laser frequency conversion applications.Because the IO₃ group has a stero-chemically active lone electron pair and a large microscopic nonlinear coefficient,iodate nonlinear optical crystals have important applications in the visible and near-infrared region.However,the development of new NLO materials still remains great challenging due to rigorous requirements including strong second-harmonic-generation（SHG）responses,wide transparency windows,high laser damage thresholds（LDTs）,good physicochemical stabilities,and the phase-matching behavior.In this thesis,nine new iodates were obtained via introducing different anionic groups,d~0 transition-mental cations,and rare earth cations into the iodate system.Their structures and physicochemical properties were studied and theoretically calculated.Firstly,a new anhydrous rare-earth iodate fluoride Ce（IO₃）₂F₂（Pna2₁）was obtained by incorporating the most electronegative element F into iodates and regulating the synthesis conditions.Compared to the hydrated Ce（IO₃）₂F₂（H₂O）（Ima2）that has been reported,Ce（IO₃）₂F₂exhibits a larger SHG response,5.5 times that of KH₂PO₄（KDP）,and has a wider transmission range and better stability.In addition,via introducing PO₄^3-into the iodates system,the first tetravalent-metal phosphate iodate Ce（IO₃）₃（H₂PO₄）（P2₁/c）and the first divalent-metal phosphate iodate Pb₂（IO₃）（PO₄）（P2₁/n）were obtained.Ce₂（IO₃）₅Cl（P2₁/c）was synthesized via introducing Cl^-with great polarizability into iodates.Five new iodates Ca Ti（IO₃）₆（H₂O）₂（R 3?）,Sr Ti（IO₃）₆（H₂O）₂（R 3?）,Sr Sn（IO₃）₆（R 3?）,Hg Pb₄O₂（IO₄）（IO₃）₂?Hg I₃（Pnam）,and Ba₂Ce（IO₃）₈（H₂O）（Pna2₁）,were obtained using the strategy of combining d~0 transition cations,lone electron pair cations and rare earth cations with iodates.Ca Ti（IO₃）₆（H₂O）₂,Sr Ti（IO₃）₆（H₂O）₂ and Sr Sn（IO₃）₆ contain zero-dimensional（0D）[M（IO₃）₆]^2-anions,which are separated by counter cations.Ba₂Ce（IO₃）₈（H₂O）is the first non-centrosymmetric iodate containing both alkaline-earth metals and rare-earth metals.The dipole moment of Ba₂Ce（IO₃）₈（H₂O）were calculated,and the calculation shows that the polarity of Ba₂Ce（IO₃）₈（H₂O）is mainly contributed by IO₃ groups.This research has enriched the mixed ion iodate system,and a nonlinear optical material,Ce（IO₃）₂F₂,with excellent performance.