Gaweł Bartłomiej A, Ulvensøen Anna, Łukaszuk Katarzyna, Arstad Bjørnar, Muggerud Astrid Marie F, Erbe Andreas
Department of Materials Science and Engineering, NTNU, Norwegian University of Science and Technology 7491 Trondheim Norway
The Quartz Corp Strandveien 50 1366 Lysaker Norway.
RSC Adv. 2020 Aug 5;10(48):29018-29030. doi: 10.1039/d0ra05798c. eCollection 2020 Aug 3.
Fused silica crucibles are commonly used in the fabrication process of solar grade silicon ingots. These crucibles are manufactured from high purity natural quartz sand and as a consequence, their properties are influenced by the presence of water and hydroxyls in the raw quartz. In this work, diffuse reflectance IR, H magic angle spinning NMR, and Raman spectroscopy were used to investigate the influence of thermal treatment on water and hydroxyl groups in high purity natural quartz sand. Most of the water in dry sand is present in the form of closed inclusions within the quartz grains which were detected in Raman imaging studies, even after thermally treating the samples at 600 °C. Only after heating to 900 °C did this water completely vanish, most likely as a result of rupturing of the inclusions. However, newly formed OH groups, identified as isolated and hydrogen bound OH were observed as products of the reaction between water and quartz. Similarly, liquid water was observed in NMR spectra even after treatment at 600 °C while at temperatures >900 °C, only non-interacting silanol groups were present. The comparison of the temperature dependence of the IR and NMR spectra also yields insight into the assignment of the OH stretching mode region of the IR spectrum in this system. The intensity of water related bands decreases while the intensity of OH bands first increases and then decreases with increasing temperature. The band intensity of Al-rich defects as well as the characteristic feature at 3200 cm does not follow the temperature dependence of typical water peaks. It is also shown that leaching the quartz sand in HF solution helps to remove water from inclusions, likely by forming pathways for fluid flow inside the quartz grains. Milling of the samples caused formation of an additional type of hydroxyl group, possibly due to partial amorphisation of the surfaces of the quartz grains surface during the process. The results improve the basis for a knowledge-based processes development for the processing of high purity natural quartz.
熔融石英坩埚常用于太阳能级硅锭的制造过程。这些坩埚由高纯度天然石英砂制成，因此其性能会受到原始石英中水分和羟基的影响。在这项工作中，采用漫反射红外光谱、氢魔角旋转核磁共振光谱和拉曼光谱来研究热处理对高纯度天然石英砂中水分和羟基的影响。即使在600℃对样品进行热处理后，拉曼成像研究仍检测到干砂中的大部分水分以石英颗粒内部封闭包裹体的形式存在。只有加热到900℃，这些水分才会完全消失，这很可能是包裹体破裂的结果。然而，新形成的羟基，即被鉴定为孤立的和氢键结合的羟基，被观察到是水与石英反应的产物。同样，即使在600℃处理后，核磁共振谱中仍能观察到液态水，而在温度>900℃时，只存在非相互作用的硅醇基团。红外光谱和核磁共振光谱温度依赖性的比较也有助于深入了解该体系中红外光谱OH伸缩模式区域的归属。随着温度升高，与水相关的谱带强度降低，而OH谱带强度先增加后降低。富铝缺陷的谱带强度以及3200cm处的特征峰并不遵循典型水峰的温度依赖性。研究还表明，用氢氟酸溶液浸提石英砂有助于去除包裹体中的水分，这可能是通过在石英颗粒内部形成流体流动通道来实现的。样品研磨导致形成了另一种类型的羟基，这可能是由于研磨过程中石英颗粒表面部分非晶化所致。这些结果为高纯度天然石英加工的基于知识的工艺开发奠定了更好的基础。
