Coordination chemistry of Ti(IV) in silicate glasses and melts .2. Glasses at ambient temperature and pressure
Coordination chemistry of Ti(IV) in silicate glasses and melts .2. Glasses at ambient temperature and pressure
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DOI：
10.1016/0016-7037(96)00145-7
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发表时间：
1996-08-01
影响因子：
5
通讯作者：
Rehr, JJ
中科院分区：
文献类型：
--
作者：
Farges, F;Brown, GE;Rehr, JJ
在常温常压下，用X-射线吸收精细结构谱(XAFS)测定了一些钛硅酸盐和钛铝硅酸盐玻璃中Ti(IV)的配位环境。这些玻璃含有2.7-30.5wt%的二氧化钛和不同量的Na2O、K2O或CaO(5.0-38.7wt%)和Al_2O_3(0-11.9wt%)，NbO/T比值在0.07-0.81之间。基于各种含钛团簇的从头算多次散射计算，对TiXANES光谱的定量分析和对归一化XAFS振荡的非谐分析表明，Ti周围存在三种类型的原子：O第一近邻，(Si，Ti)-第二近邻和碱性第三近邻。五配位的Ti，Ti-[5]是玻璃中主要的钛物种，主要集中在钛(>；16wt%TiO2O4)中，呈扭曲的四方锥体((TiO)-Ti-[5])O-4，具有一个短的Ti=O距离(1.67-1.70+/-0.03埃)和四个长的Ti-O距离(1.94-1.95+/-0.02埃)。此外，还检测到少量的Ti-[4]，其所占比例依次为：Na玻璃>lt；K玻璃。Ti2含量最低(约3-6wt%)，NbO/T值最高的钾酸盐玻璃中，以Ti-[4]为主。Ti-[4]的相对含量按Ca玻璃>Lt；K玻璃的顺序递增。最后，Ti-[6]是一个次要物种(
The coordination environment of Ti(IV) in a number of Ti-silicate and Ti-aluminosilicate glasses has been determined by x-ray absorption fine structure (XAFS) spectroscopy at the Ti K-edge at ambient temperature and pressure. These glasses contain 2.7-30.5 wt% TiO2 and varying amounts of Na2O, K2O, or CaO (5.0-38.7 wt%) and Al2O3 (0-11.9 wt%), and have NBO/T ratios ranging from 0.07-0.81.Quantitative analysis of the Ti XANES spectra, based on ab initio multiple-scattering calculations for a variety of Ti-containing clusters, and anharmonic analysis of the normalized XAFS oscillations suggest the presence of three types of atoms around Ti: O first neighbors, (Si, Ti)-second neighbors, and alkali third neighbors. Five-coordinated Ti, Ti-[5], is the dominant Ti species in the glasses most concentrated in Ti (>16 wt% TiO2) and is located in distorted square pyramids ((TiO)-Ti-[5])O-4), with one short Ti=O titanyl distance (1.67-1.70 +/- 0.03 Angstrom) and four long Ti-O distances (1.94-1.95 +/- 0.02 Angstrom). In addition, minor amounts of Ti-[4] were detected, the proportion of Ti-[4] increasing in the order: Na glasses < K glasses. Ti-[4] is the dominant Ti species in the potassic glasses with the lowest TiO2 contents (approximate to 3-6 wt%) and highest NBO/T ratio. The relative amount of Ti-[4] increases in the order: Ca glass < K glass. Finally, Ti-[6] is a minor species (