Kleebusch Enrico, Patzig Christian, Krause Michael, Hu Yongfeng, Höche Thomas, Rüssel Christian
Otto Schott Institut, Jena University, Fraunhoferstraße 6, D-07743, Jena, Germany.
Fraunhofer Institute for Microstructure of Materials and Systems IMWS, Walter-Huelse-Straße 1, 06120, Halle (Saale), Germany.
Sci Rep. 2018 Feb 13;8(1):2929. doi: 10.1038/s41598-018-21227-x.
Glass ceramics based on LiO/AlO/SiO are of high economic importance, as they often show very low coefficients of thermal expansion. This enables a number of challenging applications, such as cooktop panels, furnace windows or telescope mirror blanks. Usually, the crystallization of the desired LAS crystal phases within the glasses must be tailored by a careful choice of crystallization schedule and type of nucleation agents to be used. The present work describes the formation of nanocrystalline TiO within an LAS base composition that contains solely TiO as nucleating agent. Using a combination of scanning transmission electron microscopy as well as X-ray absorption spectroscopy, it is found that a mixture of four- and six-fold coordinated Ti ions exists already within the glass. Heating of the glass to 740 °C immediately changes this ratio towards a high content of six-fold coordinated Ti, which accumulates in liquid-liquid phase-separation droplets. During the course of thermal treatment, these droplets eventually evolve into nanocrystalline TiO precipitations, in which Ti is six-fold coordinated. Thus, it is shown that the nucleation of nanocrystalline TiO is initiated by a gradual re-arrangement of the Ti ions in the amorphous, glassy matrix, from a four-fold towards a six-fold coordination.
基于LiO/AlO/SiO的微晶玻璃具有很高的经济重要性，因为它们通常显示出非常低的热膨胀系数。这使得它们能够应用于许多具有挑战性的领域，如炉灶面板、炉窗或望远镜镜坯。通常，必须通过仔细选择晶化程序和所用成核剂的类型来控制玻璃中所需LAS晶相的结晶过程。目前的工作描述了在仅含有TiO作为成核剂的LAS基成分中纳米晶TiO的形成。通过结合扫描透射电子显微镜和X射线吸收光谱，发现玻璃中已经存在四配位和六配位Ti离子的混合物。将玻璃加热到740°C会立即使这种比例朝着高含量的六配位Ti变化，这些六配位Ti会在液-液相分离液滴中积累。在热处理过程中，这些液滴最终演变成纳米晶TiO沉淀，其中Ti为六配位。因此，研究表明纳米晶TiO的成核是由非晶玻璃基质中Ti离子从四配位向六配位的逐渐重新排列引发的。
