Growth Of Nonlinear Optical (NLO) Crystal (Cs, Rb)B₃O₅ And Search For New NLO Materials

This dissertation mainly focuses on nonlinear optical crystals. It contains two parts. One part is growth of the crystals with known structures: In this part, growth of CRBO crystal has been studied. In addition, a method which is suitable for growing near-Rb₄Nb₁₁O_29.5–composition crystals was founded out during the research of RbNbB₂O₆ crystal growth. Another part of the dissertation is the search for new nonlinear optical crystal materials. Two new compounds with second harmonic generation (SHG) effect, BZBF and BMBF have been discovered. In the meantime, two other new similar compounds, KBa₇Mg₂B₁₄O₂₈F5 and NaBa7Mg2B14O28F5, without SHG effect have been discovered.1,CRBO Crystal GrowthThe phase transition of RbB₃O₅ around 600°C leads the growth of the stoichimetric crystal failed. Partly replacement of Rb by Cs raises transition temperature and the low temperature form of structure can be stabilized upto the crystal growing temperature. Also RbF and CsF was applied as flux in order to improve the property of the melt. Through solid-state-synthesize and XRD analysis, it was found that the simple addition of CsF,RbF caused the composition of the production to shift and B2O₃ should be added on.With careful controlling of the temperature gradient in the field of growing crystal, clear CRBO crystal has been grown from the melt with the mol-ratio of elements of Cs:Rb:F:B=(0.2-0.25):(0.75-0.8):(0.1-0.4):[(2.7-1.8)+0.79].2,Growth of Near-Rb₄Nb₁₁O_29.5–Composition CrystalThe crystal of Rb₄Nb₁₁O_29.5 collapses during cooling process after its growth. While studying the growth of RbNbB₂O₆ crystal with flux method, it was found that large crystal could be grown from the melt which was mixed with raw materials with the following mol-ratio: H3BO₃:Li₂CO₃:MoO₃:Nb₂O₅:Rb2CO₃=(1-1.4):(0.2-0.4):(0.3-0.5):0.35:(0.4-0.5). The obtained crystal is iso- structural with Rb₄Nb₁₁O_29.5. ICP-OES and ICP-MS tests have been carried out to confirm the element composition, the result is Rb:Li:Nb:Mo= 3.880:0.1057:10.00:0.1128, near the composition of Rb₄Nb₁₁O_29.5. This growth method is enlightive for growing Rb₄Nb₁₁O_29.5 crystals.3,Exploration for New Nonlinear Optical Materials Through comparing BBO, LBO and KBBF in their structure and their structure-caused nonlinear optical properties, an objective formula for new nonlinear optical materials is decided. The formula is XmYnBlOjFk (X=Na,K,Rb,Cs;Y=Be,Mg,Al,In,Zn;m,n,l=1,2;k=0,1,2). Exploration has been carried out, two new nonlinear optical materials, BZBF and BMBF was discovered. The structure of BZBF has been solved from powder X-ray diffraction data, BZBF forms in P-6 space group with cell parameters of a=5.06569(7)?, c=4.28001(7)?, Z=1. The structure of BMBF has been solved from single crystal X-ray diffraction data, BMBF forms in Cc space group with cell parameters of a=17.5922?, b=30.4975 ?, c=8.0508 ?, Z=48.4,Discovery of new compounds While studying the growth of BMBF with flux method, a new compound with the formula KBa₇Mg₂B₁₄O₂₈F5 was discovered. The structure of KBa₇Mg₂B₁₄O₂₈F5 has been solved from single crystal X-ray diffraction data in forms in C2/c space group, with the following cell parameter: a=16.638(3) A,b=13.609(3) A,c=15.214 (3)A,β=121.31(3)°,Z=4. The structure contains B7O14 group, which is a new B-O group and may help in designing new borate structures.Additionally, it is found that replacing all the K in KBa₇Mg₂B₁₄O₂₈F5 with Na, a iso- structural compound NaBa7Mg2B14O28F5 can be prepared.