| In this paper,the nonlinear optical crystal materials were explored in the phosphovanadate/fluorosilicate system by high temperature solution method and hydrothermal method.The structures were analyzed and the relationship between structure and properties was analyzed.The main work is as follows:1.Three phosphate nonlinear optical crystal materials MZnPO4（M=Li,K,and Cs）were obtained in phosphate system by high-temperature solution method.They have the same chemical formula but crystallize in different space groups.Li ZnPO4 is monoclinic and crystallizes in a non-centrosymmetric Cc space group,where a=17.29（5）（?）,b=9.77（4）（?）,c=17.19（4）（?）,β=110.9（3）°,Z=32,V=2682.9（14）（?）3.In this crystal structure,Li,Zn,and P atoms are all four-coordinated.Both Li O4 and Zn O4 tetrahedra are connected to three PO4 tetrahedra to form a unit structure of[Li P3O13]and[ZnP3O13]via sharing oxygen atom.KZnPO4 belongs to the hexagonal system and crystallizes in the non-centrosymmetric P63 space group,where a=18.15（5）（?）,b=18.15（4）（?）,c=8.50（4）（?）,Z=24,V=2400.18（15）（?）3.In this crystal structure,the PO4 and the Zn O4 tetrahedra share oxygen atoms to form rings.The rings are connected in same directions to form a two-dimensional layer,and one layer is connected with another one to form a frame structure.Cs ZnPO4 belongs to an orthorhombic system and crystallizes in a non-centrosymmetric Imm2 space group,where a=5.43（5）（?）,b=9.08（4）（?）,c=9.09（4）（?）,Z=4,V=448.8（4）（?）3.In the crystal structure,ZnPO4 tetrahedra are connected to each other to form distorted polyhedra.Polyhedra are connected by oxygen atoms to form layers.Layers are connected by oxygen atoms to form a three-dimensional framework structure.Cs atoms are filled between layers.The powder second harmonic generation（PSHG）test found that the SHG effect of Li ZnPO4 was about 2.3 times KH2PO4（KDP）and KZnPO4 is 0.2 times that of KDP.The second-order nonlinear optical effect of Cs ZnPO4 was measured to be about 0.5 times KDP,Birefringence is 0.012;Theoretical calculations and calculations of dipole moments show that the effect mainly comes from the synergistic effect of PO4 and Zn O4 tetrahedra.In addition,powder X-ray diffraction（XRD）,infrared（IR）spectra of the compound were tested to demonstrate the presence of P-O groups,thermogravimetric（TG）and differential scanning calorimetry（DSC）analysis indicate the thermal stability of the compound,and diffuse reflectance measurements showed that Li ZnPO4,KZnPO4 and Cs ZnPO4 have UV absorbing edge about 221,225 and 224 nm.2.Ba（VO3）2·H2O nonlinear optical crystal was synthesized by hydrothermal method,which belongs to orthorhombic system,space group P212121.It’s unit cell parameters with a=7.39（6）（?）,b=8.99（7）（?）,c=9.72（8）（?）,γ=90°,V=353.24（?）3.The second-order nonlinear optical effect of Ba（VO3）2·H2O was measured to be about0.5 times KDP.The powder X-ray diffraction（XRD）,infrared（IR）spectroscopy,thermogravimetric（TG）and differential scanning calorimetry（DSC）analysis,energy diffuse spectrum（EDS）properties of the material were studied.Theoretical calculations show that the compound has a relatively large band gap of 3.11 e V.3.The two phosphovanadate nonlinear optical crystal materials M（VO）2（PO4）2·4（H2O）（M=Ca,Sr）were synthesized by hydrothermal method.Ca（VO）2（PO4）2·4（H2O）belongs to the triclinic system,space group P1,unit cell parameter a=6.33（5）（?）,b=6.34（5）（?）,c=6.56（6）（?）,α=85.84（7）°,β=73.14（7）°,γ=89.94（6）°,Z=1,V=346.01（?）3;Sr（VO）2（PO4）2·4（H2O）belongs to monoclinic system,space group Cc,with unit cell parameter a=9.00（3）（?）,b=8.98（3）（?）,c=12.77（5）（?）,β=100.40（3）°,Z=4,V=483.50（?）3.Through TG-DSC analysis,it was found that the target compound has good thermal stability;At the same time,their linear and nonlinear optical properties were studied.4.Hydrothermal fluorosilicate Na2Si F6 nonlinear optical crystal material was synthesized.Na2Si F6 belongs to the hexagonal system,P321 space group,with unit cell parameter a=8.87（3）（?）,c=5.04（5）（?）,Z=3,V=344.09（4）（?）3.The structure of this compound consists of two independent [Si F6]2- octahedra and two crystallographically independent sodium cations.Due to the introduction of fluoride ions,the compound exhibits a large bandgap. |
