Syntheses and Characterization of Metal Borates and Tellurates

• Main Authors: Li-Yun Zhang, 張瓈云
• Other Authors: Kwang-Hwa Lii
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/fxgw7s

碩士 === 國立中央大學 === 化學學系 === 107 === This thesis reports two new structural compounds, Ca27[B124O202(OH)22] (1) and Ca10Na10[Te9O42](H2O) (2), were synthesized by the high-temperature, high-pressure hydrothermal method and the flux growth method in the closed system, respectively. All crystal structures were determined by the single crystal X-ray diffraction. The purity of each compound was confirmed by the good agreement between the calculated and observed powder X-ray diffraction patterns, and verified the element composition by EDS. Only compound 2 product is pure, and further characterized by IR and XPS. The space group of 1 is the centrosymmetric C2/c. The structure consists of the corner-sharing 22 membered rings, which are connected to two disordered groups, B(OH)2 and B3O2(OH), respectively. It has been found through experiments that a small amount of water is decomposed by H3BO3, which can produce borate crystals in a closed environment. The elemental ratio of 1 goes with the tendency of the composition–dimensionality ternary diagram for the CaO-B2O3-H2O systems. The space group of 2 is the centrosymmetric R3 ̅c. The structure consists of discrete linear edge-sharing octahedral trimers with the composition [Te3O14]10-, which is a new type of finite Te-O oligomer with Te6+ only. The anions groups form a hexagonal close-packed lattice with the octahedral and tetrahedral interstices being filled with Ca2+ and Na+ cations and water molecules. The octahedral trimers in every other h.c.p. layers rotate around the 31 screw axis for 120°, therefore the unit cell has a very long c axis (66.337 Å). For the syntheses of novel structural inorganic materials, this study provides good strategys, and adds more novel structural compounds to the discovery.