Smedskjaer Morten M, Mauro John C, Yue Yuanzheng
†Department of Chemistry and Bioscience, Aalborg University, DK-9220 Aalborg, Denmark.
‡Science and Technology Division, Corning Incorporated, Corning, New York 14831, United States.
J Phys Chem B. 2015 Jun 11;119(23):7106-15. doi: 10.1021/acs.jpcb.5b03520. Epub 2015 May 27.
Understanding the structural origins of cationic diffusion processes in silicate glasses is important for high-tech applications of silicate glasses. For glasses with more than one network former, transport properties such as diffusivity are often nonlinear functions of the particular distribution of these network formers, a phenomenon known as the mixed network former effect. Here, we investigate the sodium-potassium interdiffusion (D̅Na-K) and the calcium inward diffusion (DCa) in soda lime borosilicate glasses with varying silica/borate ratio but constant modifier content. Indeed, the structural organization of borosilicate glasses results in a pronounced nonlinear composition dependence of D̅Na-K and DCa (i.e., the mixed network former effect). Initial addition of B2O3 to the glass system results in a significant decrease in both diffusivities, whereas the change in diffusivity per mole of added B2O3 decreases with increasing B2O3 concentration. Besides the influences of water content and atomic packing degree, we find that 99% of the composition dependence of log D̅Na-K can be ascribed to the change in concentration of tetrahedral boron groups. This indicates that the formation of BO4/2 groups slows down diffusion processes of alkali and alkaline earth ions. Therefore, the mixed network former effect of the studied glass series is linked with the change of the concentration of tetrahedral boron groups, which is caused by the interactions between the different types of network formers.
了解硅酸盐玻璃中阳离子扩散过程的结构起源对于硅酸盐玻璃的高科技应用至关重要。对于具有不止一种网络形成体的玻璃，诸如扩散率等传输性质通常是这些网络形成体特定分布的非线性函数，这一现象被称为混合网络形成体效应。在此，我们研究了二氧化硅/硼酸盐比例不同但改性剂含量恒定的钠钙硼硅酸盐玻璃中的钠钾互扩散（D̅Na-K）和钙向内扩散（DCa）。实际上，硼硅酸盐玻璃的结构组织导致D̅Na-K和DCa呈现出明显的非线性成分依赖性（即混合网络形成体效应）。向玻璃体系中最初添加B2O3会导致两种扩散率显著降低，而每摩尔添加的B2O3引起的扩散率变化会随着B2O3浓度的增加而减小。除了含水量和原子堆积程度的影响外，我们发现log D̅Na-K的成分依赖性中有99%可归因于四面体硼基团浓度的变化。这表明BO4/2基团的形成减缓了碱金属和碱土金属离子的扩散过程。因此，所研究玻璃系列的混合网络形成体效应与四面体硼基团浓度的变化有关，而这种变化是由不同类型网络形成体之间的相互作用引起的。
