Observation of yttrium oxide segregation in a ZrO <sub>2</sub> ‐SiO <sub>2</sub> glass‐ceramic at nanometer dimensions
Le Fu, Yiren Wang, Lars Riekehr, Jan Räthel, Håkan Engqvist, Wei Xia
Abstract
Abstract Dopant segregation at grain boundaries (GBs) in ceramics has been widely reported, while whether similar segregation behavior occurs in glass‐ceramics remains unknown. The distribution of dopant in glass‐ceramics may be totally different due to the existence of glass phase. This study examines the distribution of Y 3+ ions in a ZrO 2 ‐SiO 2 glass‐ceramic. Two samples were prepared by hot pressing, yttrium oxide‐doped, and undoped 65 mol% ZrO 2 ‐35 mol% SiO 2 nanocrystalline glass‐ceramics (NCGCs). The NCGCs had the same microstructure, that is, ZrO 2 nanoparticles (NPs) embedded in an amorphous SiO 2 matrix. XRD results showed that the undoped NCGC was composed of 20.9 wt% (weight percentage) monoclinic ZrO 2 (m‐ZrO 2 ) and 79.1 wt% tetragonal ZrO 2 (t‐ZrO 2 ), while the yttrium oxide‐doped NCGC was composed of 9.6 wt% m‐ZrO 2 and 90.4 wt% t‐ZrO 2 . X‐ray energy‐dispersive spectrometry (EDS) results in scanning electron transmission microscopy (STEM) mode demonstrated that Y 3+ ions segregated both on the surface of ZrO 2 NPs and within the thin intergranular glass film (with a thickness of approximately 7 Å) between ZrO 2 NPs in the yttrium oxide‐doped NCGC. Interestingly, no obvious Y signals were detected in the amorphous SiO 2 matrix. Density functional theory calculation results showed that Y 3+ ions had a strong segregation tendency in the GB area and the segregation of Y 3+ ions increased the work of separation of GB layer. These findings provide new understanding of the segregation behavior of dopant in glass‐ceramics, which may offer useful guidance for other researchers to tailor the properties of glass‐ceramics through GB engineering.