Design,Synthesis And Characterization Of Phosphate With Non-centrosymmetric Crystal Structure

The development and utilization of deep-ultraviolet nonlinear optics(deep-UV NLO)crystals is a research hotspot in the field of nonlinear optics.Deep-UV NLO crystal can achieve full-spectrum laser output through laser frequency conversion to compensate for the deep-UV region(<200 nm)which cannot be reached by the current laser.And the devices made by deep-UV NLO crystal can greatly improve the ability of detecting threats to homeland security and precision measurement.And then,non-centrosymmetric crystal structure(NCS)is the prerequisite for NLO crystal.However,the number of NCS compounds is far less than that of central symmetric crystalline compounds,and the rational design and synthesis remain challenge.Phosphates have a wide transmission range in the deep-UV region,which meets the requirements of deep-UV NLO crystal exploration and research.Therefore,the aim of the thesis is to design and obtain NCS phosphates,and explore the relationships between NLO properties and crystal structure,chemistry composition.According to the rational design of the experiment and the improvement of the synthesis method,we have synthesized seven NCS phosphates by hydrothermal/solvothermal method.The specific results are as follows:(1)Rational design and synthesis of deep-UV NLO crystal.The known compound BaFePO4(OH)with NCS structure was applied as the prototype,F-ion with strong electron-withdrawing properties was introduced to obtain the isomorphic compound BaFePO4F.And then,Zn2+ ions with d10 orbital were introduced,and the NCS compound BaZnPO4F with deep-UV transmission band was synthesized finally.BaZnPO4F has a wide light transmission range(cut-off edge<190 nm),and SHG intensity is 0.26×KDP,It is the first potential deep-UV fluorinated orthophosphate NLO crystal.(2)Two novel phosphate compounds(Li4Na2O)A2(ZnPO4)6(A = Cs,Rb)containing various alkali metals have been obtained.The compounds have a NCS structure(Space group is P62),and the crystal structure is a three-dimensional CAN-type framework structure containing 4,6,12-MR.And the compounds have short cut-off edge(<200 nm)and large second harmonic intensity(Cs:2.89×KDP,Rb:3.60×KDP;),which are potential deep-UV NLO crystals.(3)Three novel compounds Na2BaM(P2O7)(HPO4)(M= Fe,Co,Ni)with NCS structure have been obtained by hydrothermal/solvothermal method using a high ion concentration solution as a solvent.The crystal structure of the compounds is one-dimensional chain,which the sp ace group is P21212.And both the alkali metal ion Na and the alkaline earth metal ion Ba2+ in the compound controll the spatial arrangement of the transition metal and the phosphate group to form a NCS structure.(4)The synthesis method have been improved.The traditional hydrothermal method was improved by using the hydrothermal/solvothermal synthesis method with high ionic concentration solution as solvent.Using 85 wt%phosphoric acid and TEA as solvents,and using NaF aqueous solution with different concentration to control F ion,the above seven NCS phosphate compounds were successfully synthesized.