Synthesis And Optical Properties Of Crystalline Materials Containing Antimony Oxide Salt

Nonlinear optical（NLO）materials,which can achieve the tunable laser output by frequency conversion,and expand the limited range of lasers,have important applications in optical communication,medicine,military,aerospace and many other fields.How to design and synthesize new inorganic nonlinear optical materials with large second harmonic generation,appropriate birefringence and wide transparent window is a challenging topic.Second-order NLO materials require that the compound must possess noncentrosymmetric（NCS）structure.Introducing NLO-active units,such as distortive ions with second-order Jahn-Teller effect（cations containing non-bonded stereo lone pair and d⁰transition metal ions with distorted octahedral coordination）into system is an effective strategy for achieving NCS structures.Sb³⁺cations with stereochemically active lone pair are in asymmetric coordination environments,i.e.,trigonalpyramidal Sb O₃,sphenoid Sb O₄,and square-pyramidal Sb O₅,which are conducive to the formation of acentric structures and can greatly enhance the birefringence and/or the SHG response.The thesis achieved a series of crystalline materials based on stereochemically active lone pair Sb（Ⅲ）cations and discussed their structures and properties.The specific work is as follows:1.Tetrahedral unit is a promising candidate for nonlinear optical crystals with excellent performance.Its wide band gap is beneficial to deep ultraviolet transmission,and can avoid the layered habit of crystal growth.The development of NLO materials based on non-π-conjugated SO₄tetrahedron is in a challenging but signifificantly stage.Introducing Sb³⁺cations into sulfates,a series of NLO and birefringent crystals,Sb₄O₄（SO₄）（OH）₂（1）,Sb₄O₅SO₄（2）,Sb₄O₃（SO₄）₂（OH）₂（3）,Sb₆O₆SO₄（OH）₄（4）and Na Sb₃O（SO₄）₃（OH）₂（5）were achieved.Compound 1 crystallizes in a noncentrosymmetric space group with a second harmonic generation response of～1.2times of KDP.The band gap is 4.41 e V.The calculated birefringence at 1064 nm is0.147,these characteristics make 1 a potential UV NLO material.Theoretical studies were carried out according to density functional theory.The results indicate that the stereoactive lone pair of Sb³⁺cations play a major role in the linear and nonlinear optical properties.2～5 possess centrosymmetric structures,the band gaps are 4.32 e V,3.86 e V,3.65 e V and 4.41 e V,respectively.The birefringence of 4 and 5 at 1064 nm is 0.21 and 0.041,respectively,reveals that they are ultraviolet birefringent materials.Theoretical calculations indicate the birefringence is mainly derived from the contribution of the stereoactive lone pair of Sb³⁺cations.2.Halogen ions with high electronegativity can make a huge impact in electron distribution,then can regulate the structures of compounds and improve the optical properties of materials.Introducing Sb（Ⅲ）into oxyhalide system,two compounds,Sb₃F₄O₂（OH）（6）and Sb₄O₅Cl₂（7）,were obtained.The band gaps of them are 3.41 e V and 3.62 e V,respectively.The birefringence at 1064 nm of compound 6 is 0.06,suggesting that it is an ultraviolet birefringence material.The calculations show that the birefringence mainly originates from Sb-O-F/Cl polyhedra.