Synthesis,Crystal Structures And Second Order Nonlinear Optical Properties Of Novel Materials Containing The Via Group Elements

Firstly,this dissertation summarizes the research progress of crystal materials containing the sixth main group elements.We understand that this kind of crystal materials have rich and diverse structures,excellent physicochemical properties and potential application value in the second-order nonlinear optical(SONLO)properties in the infrared(IR)range.At present,several market-oriented materials have their own limitations,and these compounds are mainly obtained by the traditional high-temperature solid-state synthesis method.However,the high-temperature solid-state synthesis method has high energy consumption,long reaction cycle and difficult to prepare pure phase.With contemporary developments in green chemistry and a rising awareness of the need for environmental protection,the use of environmentally friendly methods in the metal chalcogenide system has attracted increasing attention.Ionic liquids possess unique properties such as good ionic conductivity,low vapor pressure and high thermal stability,and have been demonstrated to be promising synthetic media in the exploration of novel crystalline zeolites,metal organic frameworks,and oxides in recent years.But ionothermal method in the synthesis of metal chalcogenides is still in the primary stage.The purpose of this artical is to design new chalcogenides with SONLO response in IR region,and obtain single crystals by ionothermal method.Generally speaking,a practical infrared nonlinear optical crystal not only needs to be crystallized in non centrosymmetric(NCS)space group,but also needs to meet the following requirements:(1)sufficient frequency doubling coefficient to improve the frequency conversion efficiency;(2)wide infrared transmission band,which should cover "3-5" and "8-12",um two atmospheric windows;(3)high laser damage threshold;(4)suitable birefringence index for good phase matching;(5)good single crystal growth habit for synthesis of large size and high quality crystals.On the one hand,metal oxides will produce stretching and bending vibration peaks in the infrared region,which is not conducive to the transmission of the synthesized compounds in the infrared region.But the covalent bond between metal and sulfur anions does not exist stretching and bending vibration in the infrared region,so it is more conducive to the transmission of the synthesized compounds in the infrared region application.On the other hand,the existence of lone pair electrons in the sixth main group cation Se4+ can easily induce the second-order Taylor effect,which makes it easier to synthesize non centrosymmetric crystal materials.Therefore,the main work is as follows:1)Synthesis,crystal structure and second order nonlinear optical properties of a novel infrared nonlinear optical crystal M2Ag3Sb3S7(M=Rb,CS)Two alkali transition metal thioantimonate crystals M2Ag3Sb3S7(M=Rb,CS)were synthesized by mild ionothermal method.Each Ag atom connects with three S atoms or four S atoms to form[AgS3]5-triangular plane or[AgS4]7-tetrahedron cluster,each Sb atom connects with three S atoms to form a triangular pyramid cluster[SbS3]3-,two[AgS3]5-triangles,one[AgS4]7-tetrahedron and one[SbS3]3-triangular pyramid form[Ag3SbS5]4-clusters by conor-shared and edge-shared mode.Each[Ag3SbS5]4-cluster was connected by a five coordinated sufer atom to form an ?[Ag6Sb2S10]8-pillar,which was connected by ?[Sb2S4]2chains to form a two-dimensional layered structure on the be plane.Rb or Cs ions dissociate between these layers and play the role of equilibrium valence state.Both compounds have a wide transmittance band(0.6-20,um),which is enough to cover the "3-5" and "8-12",um two atmospheric windows in the infrared range.The second harmonic intensity of the two compounds is 2.3 and 2.5 times that of the reference KH2PO4(KDP)and 0.5 and 0.6 times that of the reference AgGaS2,respectively.Based on the first principle calculation of density functional theory(DFT),the relationship between the optical properties and the energy band structure,density of states(DOS)distribution was analyzed.2)Facile syntheses of silver thioantimonates(?)exhibiting second-harmonic generation responses and large birefringenceTwo transition metal thioantimonate crystals,[enH][Ag2SbS3](en=ethylenediamine)and[enH2][Ag4Sb2S6]were synthesized by solvothermal and ionothermal methods,respectively.[enH][Ag2SbS3]crystallized in a non-centrosymmetric space group,which possesses a two-dimensional layered structure with the[enH]+cations dissociating between the layers.One[AgS3]5-triangular pyramid,one[AgS3]5-trigonal planar and one[SbS3]3-triangular pyramid were connect by connor-sharing sufer atoms to form[Ag2SbS3]-monolayer with alternating six membered ring and ten membered ring,and then double-layer structure is formed by sharing[AgS3]5-cluster.[enH2][Ag4Sb2S6]crystallized in a centrosymmetric space group,which is a two-dimensional layered structure with the cation ions[enH2]2+dissociating between the two-dimensional layers.One[AgS3]5-triangular pyramid,one[AgS4]7-tetrahedron and one[SbS3]3-triangular pyramid were connected by connor-sharing sufer atoms to form a six-member ring.Then theses rings were connected by sufer atoms to form a honeycomb-like[Ag2SbS3]-monolayer,and then the double-layer structure is formed by sharing[AgS4]7tetrahedron.Compound[enH][Ag2SbS3]can achieve ?-type phase matching at 1064 nm and 2100 nm.Under 1064 nm laser,the second harmonic intensity is 2.5 times that of reference KH2PO4(KDP),and 0.2 times that of reference AgGaS2 at 2100 nm.The second-order nonlinear optical source of the noncentrosymmetric compound was calculated and analyzed based on the theory of band structure and density of states distribution,and the birefringence index of the compound was also calculated.Under the same synthesis conditions,the effects of ionothermal and solvothermal synthesis methods on the structure of compounds were compared,which provided a new way to explore the synthesis of new chalcogenides.3)Ionothermal synthesis of two new thioantimonates(?)with Ag+regulationUnder the regulation of transition metal Ag+,two new metal chalcogenides Rb2Sb4S7 and RbAgSb4S7·H2O have been prepared by ionothermal method under mild temperature.The crystal structure of Rb2Sb4S7 possesses two kind of metal centers[SbS3]3-triangular pyramid and[SbS4]5-twisted tetrahedron,and form a one-dimensional(1D)cluster chain with free alkali metal cations.RbAgSb4S7·H2O possesses[SbS3]3-triangular pyramid,[SbS4]5-and[AgS4]7-twisted tetrahedrons,and exhibits a unique three-dimensional(3D)framework with six kinds of member rings(MR),free alkali metal cations and free H2O molecules.Especially,20-MR is first found in thioantimonates.The band gaps of Rb2Sb4S7 and RbAgSb4S7·H2O are 1.73 and 1.85 eV,respectively,which indicates that these two compounds can act as semiconductor materials.And the birefringences of Rb2Sb4S7 and RbAgSb4S7·H2O are calculated to be 0.182 and 0.065 at 1064 nm,respectively.Under the same synthesis condition,the addition of transition metal Ag+has a great influence on their crystal structures and band gaps,which provides the possibility for designing and synthesizing diversified chalcogenides under ionothermal conditions.4)Multinary thioantimonates(?)with d10 transition metals:ionothermal synthesis,crystal structures and physical propertiesTwo new multinary thioantimonates(?)with d10 transition metals(TMs)Rb2HgSb4S8 and CdSb2S4 have been prepared by environmental-friendly ionothermal method.Rb2HgSb4S8 has[HgS4]6-tetrahedrons,[SbS3]3-triangular pyramids,free Rb+cations,and exhibits a unique two-dimensional(2D)cluster double-layer architecture.CdSb2S4 is the first Cd2+-containing multinary thioantimonate(?).It has two kinds of metal centers[SbS3]3-and[SbS4]5-,and exhibits a novel 2D ?[Sb2S4]2-cluster layer,which is constructed by disulfide bonds linking with ?[Sb4S8]4-chains.Remarkably,free Cd2+cations as well as disulfide bonds are first found in thioantimonates.The band gaps of Rb2HgSb4S8 and CdSb2S4 are 1.82 and 1.57 eV,respectively,which indicates that these compounds are potential semiconductor materials.The birefringences of them are calculated to be 0.128 and 0.143 at 1064 nm,respectively.Theoretical studies using density functional theory have been implemented to further understand the relationship between their band gaps and crystal structures.5)Synthesis,structure and nonlinear optical properties of fluoroseleniteThe selenite crystal compound containing Se4+ cations was synthesized by hydrothermal method.At the same time,F-and stereoscopic active lone pair electrons containing Bi3+were introduced into the system.A new crystal material BiSeO3F with large second-order nonlinear response was synthesized successfully.In this crystal structure,the adjacent[BiO5F2]9pentagonal bipyramid forms a zigzag chain through connor-sharing an oxygen atom.These zigzag chains are then linked to form a layer along the b-axis by sharing an O2-ion and an F-ion.At the same time,along the c-axis,these chains form another layer through[SeO3]3-linkage.Then these layers are connected vertically by edge-sharing zigzag chains to form a three-dimensional structure.The second harmonic measurement of BiSeO3F powder shows that it has a strong signal in the visible and near-infrared region.The second harmonic generation efficiency of BiSeO3F is about 13.5 × KH2PO4(KDP)and 1.1 × KTiPO4(KTP)at 1064 nm and 2100 nm,respectively.Type-I phase matching can be achieved in both bands.Based on the first principle theory of density functional theory,the energy band structure,density of states distribution and tensor of nonlinear optical properties of the compounds are calculated and analyzed.