Synthesis And Growth Of Nonlinear Optical Vanadiate Crystal

In recent years, researches have been paid much attention to researches on nonlinear optical crystal materials, thus researches on nonlinear optical vanadate crystal began to attract professor's eyes. Transition metal ions with a high-valent d0 electronic configuration was affected by second-order Jahn-Teller, in the ideal octahedral field that containing MO6n-, HOMO and HOLO changing their own orbital makes HOMO energy level lower and makes the system more stable, which makes MO6n- group along the octahedron occurs for two times, three times or even four times to form the asymmetric structure that is conducive to the formation of noncentrosymmetrical crystal structure. Vanadium can easily combine with oxygen to form vanadium-oxygen polyhedron and prone to distortion, so vanadium as important element of second-order nonlinear crystal materials should be widely concerned.It has been reported the structure of K₃V₅O₁4, a kind of infrared nonlinear optical crystal, but few scholars did research on its properties until recent years. Using the Bridgman-Stockbarger method to make a research experiment on its growth, we have succeeded in synthesizing polycrystalline materials by high-temperature solid-phase method and liquid-phase method. After X-ray powder diffraction pattern confirmed that the high-temperature solid-phase synthesis can make relatively high purity of raw materials, which can be used in growthing the K₃V₅O₁4. The crystals grow to be a multi-crystal rod, but which contains a relatively good quality single crystal flakes that can be used as the seed of growth. The obtained crystals were measured including light, heat, SHG and other properties, results showed that: K₃V₅O₁4 transmission rate is up to 85% in the 1000-4000cm-1; its melting point is 413℃determined by using TG-DTA; the second harmonic output intensity of K₃V₅O₁4 was 3.7 times as large as KDP, which is a good second-order nonlinear optical crystal. In addition, I make an in-depth analysis on the composition of the crystals.A new compound of Rb₃V₅O₁4 has been prepared by reaction of Rb2CO3 and V2O5, through the high-temperature solid-phase method, which was similar to K₃V₅O₁4. The X-ray single-crystal showed that Rb3V5014 crystallizes in a triclinic space group P31m with it can be viewed as a layered compound of V50143- unit that are capped by Rb+. By X-ray powder diffraction patterns, it is confirmed that the resultant of reaction is synthetic Rb3V5014 pure phase. Rb₃V₅O₁4 is noncentrosymmetric crystal structure, after Second harmonic generation measurements, nonlinear optical coefficient was about 4.2 times of the KDP: its transmission rate is also up to 80%; its melting point is 398℃.A new compound of C_sV₂O₅ has been prepared by reaction of Cs2CO3 and V2O5, through high-temperature solid-phase method, the resultant of reaction is a kind of new compound C_sV₂O₅. C_sV₂O₅ belongs to orthorhombic system, Ima2 space group , unit cell parameters: By paramagnetic resonance test and magnetic test, it is proved that the compound contains a series of tetravalent vanadium atoms, thus V4+and V5+are existed by combining with oxygen to form tetrahedral structure of vanadium oxide. The obtained crystals were measured including light, heat, SGH and other properties, results showed that: C_sV₂O₅ transmission rate is up to 85% in the 1000-4000 cm^-1; its melting point is 455℃determined by using TG-DTA; the second harmonic output intensity of C_sV₂O₅ was 8.1 times as large as KDP, which can serve as a potential infrared nonlinear optical crystal materials. In addition, a growth experiment of it has made by using the Bridgman-Stockbarger method.