Effect of temperature and TiO2 content on the structure of Na2Si2O5Na2Ti2O5 melts and glasses
Effect of temperature and TiO2 content on the structure of Na2Si2O5Na2Ti2O5 melts and glasses
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DOI：
10.1016/0016-7037(94)00290-3
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发表时间：
1995
影响因子：
5
通讯作者：
B. Mysen;D. Neuville
中科院分区：
文献类型：
--
作者：
B. Mysen;D. Neuville
在25 ~ 1316°C的温度范围内，用显微拉曼光谱原位研究了Ti ~（4+）与玻璃阴离子结构的相互作用，并沿着Na_2Si_2 O_5 → Na_2 Ti_2 O_5的连接处进行了研究。在无钛端元体系中，（1）2 Q3惠Q2+ Q4能很好地描述阴离子平衡。Ti4+溶液稳定了另外一个单元Q1。这种结构变化需要一个额外的表达式，（2）2 Q2惠Q3+ Q1，来表示平衡。反应1的Δ Hx 1为<$24 kJ/mol，而反应2的Δ Hx 1为<$−40 kJ/mol。这些值不同于类似的Na 2Si 2 O 5 → Na 2（NaAl）2 O 5体系（Mysen和Frantz，1994 a），其中含Al熔体的Δ Hx 1为−11-−14 kJ/mol，反应2的Δ Hx 1为17-33 kJ/mol，取决于Al（Al + Si）。TiO 2浓度的增加与Q2和Q1结构单元的丰度呈正相关，而与Q3和Q4结构单元的丰度呈负相关。在等效的Al系统中（Mysen和Frantz，1994 a），Q2、Q1和Q4呈正相关，Q3丰度与Al 2 O3的增加呈负相关。含钛玻璃和熔体的拉曼光谱与Ti ~（4+）在至少三个不同的结构位置（Si ~（4+）惠Ti ~（4+）取代、TiO ~（2+）型团簇和Ti ~（4+）作为网络改性阳离子）上是一致的。这种行为取决于温度和TiO 2浓度。四面体配位的Ti4+的分数从≤ 3.5mol%TiO2时的近0%增加到玻璃中的近80%，并在20mol%TiO2时熔化。将温度升高到玻璃转变区间（400-500°C）以上导致四面体配位中的Ti 4+分数降低10-30%。当温度超过800-900°C时，这种趋势就会逆转。有人建议，温度和组成依赖的结构行为的Ti 4+在熔体中可能会反映在熔体性质，如粘度，热膨胀，和热力学性质的不寻常的行为。
The interaction of Ti4+with the anionic structure of glasses and melts along the join Na2Si2O5Na2Ti2O5has been examined in situ at temperatures between 25 and 1316°C with microRaman spectroscopy. In the Ti-free endmember system the expression, (1) 2Q3⇔ Q2+ Q4describes the anionic equilibria adequately. Solution of Ti4+stabilizes an additional unit, Q1. This structural change requires an additional expression, (2) 2Q2⇔ Q3+ Q1, to represent the equilibria. The ΔHx1for reaction 1 is ∼24 kJ/mol, whereas that for reaction 2 is ∼ −40 kJ/mol. These values differ from those in the analogous Na2Si2O5Na2(NaAl)2O5system (Mysen and Frantz, 1994a), where ΔHx1for Al-bearing melts is −11–−14 kJ/mol, and that of reaction 2 is 17–33 kJ/mol, depending on the Al (Al + Si) . Increasing TiO2concentration is positively correlated with the abundance of Q2and Q1structural units, whereas those of Q3and Q4are negatively correlated. In the equivalent Al-system (Mysen and Frantz, 1994a), the Q2, Q1, and Q4are positively correlated and the Q3abundance is negatively correlated with increasing Al2O3. The Raman spectra of Ti-bearing glasses and melts are consistent with Ti4+in at least three different structural positions (Si4+⇔ Ti4+substitution, clusters perhaps of TiO2type, and Ti4+as a network-modifying cation). This behavior depends on both temperature and TiO2concentration. The fraction of tetrahedrally coordinated Ti4+increases from near 0% for ≤3.5 mol% TiO2to nearly 80% in glasses and melts with 20 mol% TiO2. Increasing temperature above that of the glass transformation interval (400–500°C) results in a 10–30% decrease in the fraction Ti4+in tetrahedral coordination. As the temperature is raised beyond 800–900°C, this trend reverses. It is suggested that the temperature- and composition-dependent structural behavior of Ti4+in the melts might be reflected in unusual behavior of melt properties such as viscosity, thermal expansion, and thermodynamic properties.