Three New Alkaline Beryllium Borates LiBeBO3, Li6Be3B4O12, and Li8Be5B6O18 in the Ternary Phase Diagrams Li2O–BeO–B2O3

The phase diagram in the Li2O–BeO–B2O3 system has been systematically investigated by the methods of visual polythermal analysis, spontaneous crystallization, and X-ray diffraction. Three new alkaline beryllium borates, namely, LiBeBO3, Li6Be3B4O12, and Li8Be5B6O18, were synthesized with molten fluxes based on Li2O–B2O3 solvent in this system. All of the materials are centrosymmetric. The similarity of the fundamental building block of the title compounds has been compared. Thermal analysis and powder XRD studies were applied to determine phase relation and their incongruent melting behavior. The UV–vis diffuse reflectance spectroscopy demonstrated that the UV cutoff edges of the aforementioned materials are all below 200 nm.

本研究采用可视多热分析、自发结晶法及X射线衍射（X-ray diffraction）法，对Li₂O–BeO–B₂O₃体系的相图进行了系统探究。本体系中以Li₂O–B₂O₃为熔剂，成功合成了三种新型碱金属铍硼酸盐，分别为LiBeBO₃、Li₆Be₃B₄O₁₂及Li₈Be₅B₆O₁₈。所有合成产物均具有中心对称性。本研究对上述目标化合物的基本结构基元的相似性进行了对比分析。通过热分析与粉末X射线衍射（X-ray powder diffraction）手段，明确了该体系的相关系及其不一致熔融行为。紫外-可见漫反射光谱（ultraviolet-visible diffuse reflectance spectroscopy）测试结果表明，前述三种材料的紫外截止边均低于200 nm。