Explorations And Properties Of Alkali Metals Complex Optical Crystal Material

Borates have been widely used in the field of optical materials due to their great structural variety and extraordinary physical and chemical properties. In this paper, the main purpose of this dissertation is to design, synthesize and grow novel photoelectric functional crystal materials, especially to explore the deep-ultraviolet birefringent crystal and alkali metal crystal materials. In this work, we followed the following idea and strategies:（1） following the anionic group theory and introducing the alkali metal elements which is without the d-d electron transition to explore the UV-DUV materials;（2） exploring the alkali metal compounds by high temperature solution method;（3） introducing the covalence cation to obtain the compound that contain isolate B-O group;（4） following the P.Becker theory, adjust the rate of the B/O to obtain isolate plane unit.1. NaBO₂: the deep-ultraviolet birefringent materials.According to the anionic group theory and bring in the alkali metal cations we have fully developed a new deep UV birefringent crystal of NBO. A single crystal of NBO with dimensions of 15 mm × 15 mm × 6 mm was grown from its stoichiometric melt in 1 day for the first time, which is a greatly improve of crystal growth method. These NBO crystals achieve desirable optical properties with a large birefringence（Δn = 0.2653-0.0763） from the IR（3.35 μm） to the deep UV（180 nm） range. NBO melts congruently with no phase transitions and possesses a lower growth temperature among the birefringent materials. By the pulling method the crystal is beneficial for the growth of large with the high quality optical. The good chemical stability and mechanical properties make it easier to be processed by cutting and polishing.2. Synthesis, crystal structure and properties of LiNaB8O13, α- and β-LiKB₈O₁₃Borates have rich structure types, which is the preferred system to explore novel compounds. B atoms combine O atoms can be form BO₃ and BO₄. Further the BO₃ and BO₄ can form polymerization boron oxygen groups, including the isolated island, cyclic, chain, layered and three-dimensional network structure, B-O structure with structural diversity allow us to explore new borate provides rich resources of structure type. The LiNaB₈O₁₃, α- and β-LiKB₈O₁₃ have three network with four connections. It is worth to note that [B8O13]2-consist of [B₅O₁₀]^5- and [B₃O₇]5-, which have four terminal oxygens with similar distribution, which is form A2B8O13（or AA’B8O13） system, that is the reason of high and low temperature phase. Two pairs of terminal oxygens are approximately perpendicular to each other. And[B₅O₁₀]^5- can be seen as two [B₃O₇]5- linked together by sharing one [BO₄]5-. Hence, the 4-c [B₅O₁₀]^5- and [B₃O₇]5- can assemble together flexibly and lead to versatile structure. One [B₅O₁₀]^5- are connected with four [B₃O₇]5- in LiNaB₈O₁₃ and β-LiKB₈O₁₃, which connection manner is denoted as Mode I. One [B₅O₁₀]^5- are surrounded by two [B₃O₇]5- and two [B₅O₁₀]^5-, denoted as Mode II. Furtherly, the Mode I can be divided into two types, based on whether the directly connected [BO₄]5- in [B₃O₇]5- links with two terminal oxygens in one B-O ring of [B₅O₁₀]^5-（Mode IA） or two（Mode IB）. Similarly, Mode IIA and Mode IIB were separated by whether two [B₃O₇]5- are located at one ring of [B₅O₁₀]^5-（Mode IIA,） or two（Mode IIB）. All octoborates mentioned above can also be described as a 3D 4-c network in the topological view with the Schl?fli symbol.3. Linear and Nonlinear Optical Properties of Aluminum Borate Crystal Al₅BO₉By introducing strong covalent ions in aluminum borate compounds to obtained non-centrosymmetric Al₅BO₉ with containing primitives isolated compounds. The fundamental building blocks of the structure are BO₃ triangles, Al O₄ tetrahedra and Al O6 octahedra. Since Al₅BO₉ only consists of strong covalent B-O and Al-O bonds, it is worth investigating the structure-optical property relationship thoroughly, especially the linear and nonlinear optical properties. To gain further insight into the origin of the nonlinear optical response of Al₅BO₉, the electronic structure calculations, SHG-weighted electron density and dipole moment of polyhedra were analyzed in detail. All evidences deduced from calculated results indicate that the SHG contribution from the Al-O polyhedra is more pronounced than that of the BO₃ group in Al₅BO₉, which is anticipated to open a window for the search and design of new inorganic materials.4. Synthesis, crystal structure and properties of Li₂Na₂B₂O₅, Li6 Zn B4O12 contain isolate B-O unitBased on the research of P. Becker, isolated BO₃ groups could exist in the ratio of cations : boron > 1, which means that it is feasible to obtain borates with isolated BO₃ groups by increasing the proportion of cations in experiments.According to Chen’s anion group theory, the B-O plane unit have the π-conjugated configuration and strongly anisotropic polarization, which will favor the large SHG response and birefringence. Therefore, my first part work is to combine the isolated B-O plane unit with different types of cations. By using this strategy, we have synthesized several borates with isolated B2O5 and BO₃, which consists of Li₂Na₂B₂O₅ and Li6 Zn B4O12.