Designs,Syntheses,and Second-Order Nonlinear Optical Properties Of Metal Selenites And Tellurites Containing Fluorin

Nonlinear optical(NLO)crystal as a class of important photoelectric functional materials,have been widely used in modern photoelectron technology both for civilian and military applications.Among the NLO materials,metal selenites and tellurites are very important.The presence of the active lone-pair electrons of Se4+ and Te4+ cations which are susceptible to the second-order Jahn-Teller(SOJT)distortions can serve as a structure-directing agent and aid in the formation of novel structures with interesting physical properties.In this thesis,our work focused on the exploration of new NLO materials in metal selenites and tellurites containing fluorin.On the one hand,in order to enhance the second harmonic generation(SHG)responses of metal selenites,the idea of aliovalent substitution is applied to its structural design:substitution of iodate groups by selenite groups and oxo anions by fluoride or hydroxide anions.Such metal selenites may be able to maintain a similar topology as the parent metal iodates,which have properly aligned polar units.On the other hand,we introduced fluoride ions into the metal selenites and tellurites containing d0 transition metal(TM)ions(V5+,Mo6+,W6+),in order to obtain the compouds with novel crystal structures and high SHG responses.In this thesis,nine new metal selenites or tellurites have been synthesized by hydrothermal reactions.Their structures have been determined by single crystal X-ray diffraction studies and further characterizations of IR spectra,powder X-ray diffraction and energy dispersive X-ray spectroscope(EDS)have also been preformed.Moreover,their thermal and second-order nonlinear optical properties have also been studied.The main results are summarized as follows:(1)We designed selenite-based high-performance SHG materials by the aliovalent substitution of polar metal iodates with large SHG responses.On the basis of this idea,BiOIO3 with a strong SHG efficiency(12.5 X KDP)was chosen as the parent compound.Substitutions of iodate and oxo anions by selenite and fluoride anions,respectively,led to the discovery of BiFSeO3(1),which exhibits a very large SHG response of about 13.5 times that of KH2PO4(KDP)and was synthesized under facile hydrothermal conditions.Furthermore,we introduced In3+ into this system,and substituted the parent compound BiOIO3 with SeO32-and F-to synthesize the compound InFSeO3(2),which crystallized in the centrosymmetric space group,and does not have SHG responses.(2)Seven new metal selenites and tellurites containing d0-TM ions,namely,SrVSeO5F(3)?BaVSeO5F(4)?BaWTeO5F2(5)?BaMoTe05F2(6)?BaMo2Te2010F2(7)?VTeO4(OH)(8)and Ba2V4O8(Te3O10)(9),have been successfully synthesized by hydrothermal reactions.In the structures of compounds 3-7,we introduced F-into the d0-TM coordinate environment which results not only new structures but also novel compounds with NLO property.Among these seven compounds,7 and 8 crystallize in noncentrosymmetric space group and exhibit SHG response of approximately 7.8 and 0.3 times that of KDP,respectively.