Syntheses,Growth And Characterization Of New Nonlinear Optical Crystals Of Zinc-borates And Oxyhalides

As an important photoelectric functional material,Ultraviolet(UV)or Deep-UV nonlinear optical crystal has special significance for the output of different frequencies of solid-state laser.Aiming at the design and synthesis of new UV or deep UV nonlinear optical crystals,through the structural optimization of KBe₂BO₃F₂(KBBF)and the band gap engineering of perovskite solar cells,ten kinds of noncentrosymmetric structures have been successfully designed and synthesized.The performance characterization of these structures shows that four of these materials have good nonlinear optical effects,which are potential UV and deep UV nonlinear optical crystals.1.Syntheses and characterization of new materials based on classical KBBF structure modelKBBF is the only deep UV nonlinear optical crystal whose output wavelength is less than 200 nm at present,but it has obvious layered growth characteristics and needs high toxicity Be O as raw material to grow the crystal,which limits its wide application.In this study,we use Zn²⁺instead of Be²⁺to avoid the use of highly toxic Be O,and design and synthesize a series of Zn-borate compounds with KBBF like structure,including CsZn₂(BO₃)F_2,CsZn₂(BO₃)Cl₂and CsZn₂(BO₃)FCl.The results show that the UV cut-off edge of these compounds is less than 190 nm,and CsZn₂(BO₃)FCl shows the largest frequency doubling effect in KBBF family,about 3.5×KDP.At the same time,this compound is also the first one with double halogen compound structure in KBBF family,which has certain guiding significance for enhancing SHG response of KBBF family compounds.2.Synthesis of the fluorotellurite by band gap engineeringBy introducing the energy band engineering of perovskite solar cells into the tellurite system,we have successfully synthesized Ba F₂Te F₂(OH)₂ with pseudo-Aurivillius structure.Due to its unique structure,the maximum band gap(5.9 e V)in tellurite and tellurite is obtained,and achieve a desired balance among the wide band gap,large SHG response and suitable birefringence,i.e.Ba F₂Te F₂(OH)₂ has a short UV cut-off edge(?205 nm),large SHG response(?3×KDP)and moderate birefringence(?0.078@visible region)and be a promising UV NLO crystal.3.Synthesis and characterization of Pb₁₀O₄(BO₃)₃I₃During our research,we have also found several new compounds with interesting crystal structures.A new non-centrosymmetric borate iodide of Pb₁₀O₄(BO₃)₃I₃ has been synthesized.Interestingly,in this structure,some oxygen atoms are coordinated by four Pb²⁺cations to form[OPb₄]groups,rather than directly connecting with B³⁺atoms.This compound is belonged to a new type of borate iodide,oxyborate iodide.