Syntheses And Properties Of Rare Earth Borate Nonlinear Optical Crystals Based On BO₃ Groups

UV nonlinear optical(NLO)crystals play an increasingly important role in the field of solid-state lasers.In this paper,new UV/deep UV nonlinear optical materials were design and synthesize by combining planar BO₃ groups with rare earth cations(Sc³⁺,Y³⁺,La³⁺).Finally,several borates have been successfully designed and synthesized by traditional high-temperature solid-phase methods.The relationship between the electronic structures and nonlinear optical properties of the compounds was also studied based on density functional theory.Additionally,by adjusting the ratio of anions and cations in the structure,four new phosphates were successfully synthesized.The detail of this paper were as follows:1.UV nonlinear optical crystal K₁₅La₇(BO₃)₁₂ crystallizes in the monoclinic non-centrosymmetric space group Pn.K₁₅La₇(BO₃)₁₂ exhibited 2D[La₁₂B₇O₇₈]_?layer composed of La O₈ polyhedra and BO₃ groups,and the layers were linked by BO₃groups to build a three-dimensional framework.It has strong second harmonic generation(SHG)effect,wide transmission range and high thermal stability.It was a potential material of ultraviolet nonlinear optical materials.2.K₅Mg₂La₃(BO₃)₆was synthesized by introducing alkaline earth metal into K₁₅La₇(BO₃)₁₂.It crystallizes in the trigonal non-centrosymmetric P31m space group.It exhibited two-dimensional honeycomb 2D[La BO₃]_?layer composed of La O₉polyhedron and B(1)O₃ units through shared vertices.Further,the layers were connected by B(2)O₃ groups to build the whole structure.The test indicated that K₅Mg₂La₃(BO₃)₆ shows about 3.1×KDP with phase matching,UV cut-off edge less than 200 nm,and high thermal stability.Those indicated that K₅Mg₂La₃(BO₃)₆ was a potential material of deep nonlinear ultraviolet optical crystal.3.Four new compounds Ba₂Mg Y₂(BO₃)₄,Ba₂Cd Y₂(BO₃)₄,Ba₂Cd Sc(BO₃)₃and Cd₃Sc(BO₃)₃were successful synthesized and they all contain isolated BO₃ groups.Their structure contains different dimensions of rare earth boric acid skeleton.Ba₂Mg Y₂(BO₃)₄ and Ba₂Cd Y₂(BO₃)₄ were isostructural and their structures can be described as one-dimensional chain structure formed by Mg O₆/Cd O₆ and YO₇/YO_6.The chains further connected BO₃ groups to form a three-dimensional network structure.Ba₂Cd Sc(BO₃)₃ structure presented a 2D[Cd Sc(BO₃)₃]_?layer composed of Cd O₆,Sc O₆,and BO₃groups.Cd₃Sc(BO₃)₃ presented a one-dimensional firewheel-like[Sc B₃O₉]chain composed by Sc O₆ and BO₃group.Thermal property analysis indicated that they all have high thermal stability and wide transmission range.4.Four new phosphates K₆Bi₁₃(PO₄)₁₅,K₅Bi(P₂O₇)₂ and A₅Bi₅(PO₄)₄(P₂O₇)₂(A=K,Rb)were synthesized with different degrees of polymerization P-O groups.Structural comparison indicated that the Bi/P ratio has an important influence on the degree of PO₄ groups polymerization.Thermal analysis presented that K₅Bi(P₂O₇)₂and Rb₅Bi₅(PO₄)₄(P₂O₇)₂ were congruent compounds,while K₆Bi₁₃(PO₄)₁₅ was incongruent compound.Additionally,Cd₄In O(BO₃)₃ were successfully synthesized by substituted Re³⁺in Ca₄Re O(BO₃)₃ with In³⁺.Cd₄In O(BO₃)₃ crystallizes in monoclinic system,non-centrosymmetric Cm space group.It has a three-dimensional framework composed of common vertices of Cd O₆,Cd O₈,and In O₆polyhedra,and BO₃ groups embedded in the framework.In addition,Cd₄In O(BO₃)₃ has a strong SHG effect about 3.1×KDP and moderate birefringence 0.077@1064 nm,which is a new visible nonlinear optical crystal.This part has reference value for the synthesis of material with different polymerization degree of PO₄ groups.