若干钠锗酸盐晶体和熔体的温致结构变化及其锗配位数的拉曼光谱研究

摘要

本文测定了Na4GeO4、Na2GeO3、Na2Ge4O9和Na4Ge9O20等晶体从273 K到1413 K升温及熔体的拉曼光谱,结合分析金红石型GeO2的相关结构和光谱,研究了其微结构单元在升温过程中的变化、熔体中的形态和锗的氧配位数及其温致变化.Na4GeO4和Na2GeO3晶体结构单元为GeO4四面体,在升温过程及其熔体中锗维持四配位.Na2Ge4O9和Na4Ge9O20晶体结构单元为GeO4四面体和GeO6八面体共存,升温过程中,GeO6八面体将发生结构转变,在熔融状态全部转变为GeO4四面体,并产生与钠离子等摩尔分数的非桥氧,在熔体中锗的氧配位数为4.研究还表明,桥氧的对称弯曲振动模可以反映不同微结构单元间的连接,并且随着温致结构的变化而产生特征性的变化.%Temperature dependent structure evolutions of Na4Ge04, Na2Ge03, Na2Ge409 and Na4Ge902ocrystals from 273 to 1413 K and their melts and germanium coordination are studied by high temperature Raman spectroscopy combining with the microstructure and spectrum study of rutile type GeO2. The results indicate that there are only tetrahedral GeO4 units in Na4 GeO4 and Na2Ge03 crystals, remaining unchanged with the increasing temperature. The coordination number of germanium for both Na4 GeO4 and Na2 GeO3 melts is four. In both Na2 Ge4 Og and Na4 Ge9 O20 crystals, octahedral GeO6 units coexist with tetrahedral GeO4 units. With the increasing temperature, GeO6 units transform into GeO4 units and non-bridging oxygen is formed while the coordination number of germani-um is four in both melts of Na2Ge409 and Na4Ge902o. The results also demonstrate that bridge-oxygen symmetric bending vibration modes could reflect the linkage types between different units and changed dramatically with the temperature dependent structure evolution.