Synthesis of Rare Earth Polyborates Using Molten Boric Acid as a Flux

• Published in: Chemistry of materials Vol. 14; no. 12; pp. 4963 - 4968
• Main Authors: Li, Linyan, Lu, Peichao, Wang, Yaoyang, Jin, Xianglin, Li, Guobao, Wang, Yingxia, You, Liping, Lin, Jianhua
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.12.2002
• Subjects: Chemistry; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Inorganic chemistry and origins of life; Inorganic compounds; Physics; Preparations and properties; Salts; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Lanthanide Borates; Hydrogen Borates; Phase diagram; Photoluminescence; Experimental study; X ray diffraction; Inorganic compound; Lanthanide compound; Anhydrous compound; Optical properties; Chemical preparation; Hydrates; Crystalline structure
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm0203870

Hydrated rare earth hexaborates H3LnB6O12 (Ln = Sm−Lu) have been synthesized by using molten boric acid as the reaction medium. H3LnB6O12 decomposes at certain temperatures to form anhydrous pentaborates LnB5O9 (Ln = Sm−Er) or orthoborates LnBO3 (Ln = Tm−Lu). The crystal structures of the hexaborates and pentaborates have been determined by single-crystal and powder diffraction techniques. The hydrated hexaborates H3LnB6O12 crystallize in a trigonal structure in the space group R3c, which contain a six-membered ring B6O15 as a fundamental fragment. Anhydrous pentaborates LnB5O9 crystallize in a tetragonal structure that is built up with B4O9 and BO3. LnB5O9 decomposes at higher temperature to metaborates (Ln = Sm−Tb) and orthoborates (Ln = Dy−Er). A phase diagram is presented that shows the stable range of both H3LnB6O12 and LnB5O9. The luminescent property of the europium-doped GdB5O9 was studied.