Design,Growth And Performance Evaluation Of Alkali Metal Borate And Silicate UV Photoelectric Functional Crystals

Crystal materials can generate rich linear and nonlinear performance by the periodic lattice structure.At the moment,optical crystal materials,particularly that the optical crystal with the cut-off edge as low as ultraviolet（UV）（200-400 nm）and deep ultraviolet（DUV）（<200 nm）have become a research focus in the field of international materials science.In this article,the main research directions are borate and silicate optical crystals,which cover the screening of structural elements,the exploration of new photoelectric functional crystals,crystal growth and performance evaluation.The main research contents are as follows:（1）Crystal growth and performance evaluation of K₃Sr₃Li₂Al₄B₆O₂₀FThe centimeter single crystal of K₃Sr₃Li₂Al₄B₆O₂₀F were grown by top seed method.The transparent wafers of（001）and（010）directions were cut.The transmission spectra,temperature birefringence,laser damage threshold,coefficient of thermal expansion and the laser output of532nm were tested by（001）wafer.And the quadruple-frequency laser of 1064nm was output using（010）wafer.The transmission spectra of K3Sr3Li2Al4B6O20F is 190 nm,the birefringence is not sensitive in the range of 20-100℃,about 0.061@532 nm.The laser damage threshold is18.5GW/cm² in 1064 nm 10μs.The calculated walk-off angle is small,between 1.9°-2°.The test results show that K₃Sr₃Li₂Al₄B₆O₂₀F is a good quadruple-frequency non-linear optical crystal.（2）Crystal growth and performance evaluation of K₅B₁₉O₃₁ crystalA transparent K₅B₁₉O₃₁ single crystal was obtained by the top seed method.The powder X-ray diffraction pattern（PXRD）,infrared spectrum,transmission spectrum,and thermogravimetric differential thermal spectrum（TG-DSC）were tested.The band structure diagram of K₅B₁₉O₃₁ was obtained and the birefringence was calculated.K₅B₁₉O₃₁ has a band gap of 5.43 eV and a cut-off edge as low as 180 nm.XRD and TG-DSC spectra show that K₅B₁₉O₃₁ is a molten compound with the same composition.Calculations show that K₅B₁₉O₃₁has a good birefringence（0.05@1064 nm）,indicating that it is a good deep ultraviolet birefringent crystal.（3）Synthesis and performance evaluation of M₆Si₁₀O₂₃（M=K,Rb,Cs）series of nonlinear optical crystalsFour types asymmetrical silicates in M6Si10O23（M=K,Rb,Cs）system were synthesized.Performance tests were performed on Rb₆Si₁₀O₂₃ and Cs₆Si₁₀O₂₃.It was found that Rb₆Si₁₀O₂₃is phase-matched and has a large frequency-doubling effect,approximately 1.2 times KDP.Although Cs₆Si₁₀O₂₃ is not phase-matched,it exhibits a large frequency doubling effect of 1.2times KDP.After investigation,it was found that Rb₆Si₁₀O₂₃ has the largest frequency-doubling effect in the phase matching silicates that have three-dimensional（3D）Si-O groups.After diffuse reflection testing,it was found that the cutoff edge of both compounds was below 190nm,reaching the deep ultraviolet region.The results show that Rb₆Si₁₀O₂₃ is an excellent UV nonlinear optical crystal material.（4）Synthesis and performance evaluation of K_0.64Cs_0.36SiF₇ trans-perovskite optical crystalK_0.64Cs_0.36SiF₇ is a new type of trans-perovskite optical crystal,crystallized in the square space group P4/mbm.In this crystal structure,[FK₄(Cs_0.36/K_0.64)₂]octahedron was used to replace the[TiO6]octahedron cover in the perovskite,and[SiF6]octahedron was used to replace the Ca2⁺in the perovskite.Structural analysis found that the compound has a special disorder place and disorder ratio compared with its compounds of the same series.A series of optical tests and thermal tests were performed on the polycrystalline powder,and the influence of the occupancy on the crystal properties was compared using first-principles calculations.