Electron Microscopy Study of Solute Segregation Process in an Oxide Grain Boundary

Yttria stabilized zirconia (YSZ) is a technologically important ceramic with diverse applications. However, the structure and chemistry at the atomic scale need to be well-controlled to optimize the macroscopic properties and behaviour. In YSZ, Y³⁺ tends to segregate to grain boundaries in a substitutional manner as in the bulk. Currently, little is known on the segregation process and the conditions that trigger segregation. A novel bicrystal fabrication process was developed to fabricate specimens without Y³⁺ segregation. As a model system, the grain boundary geometry selected for this study is Σ3 {111}<110>. To induce grain boundary segregation, the specimen was annealed at various temperatures and their structure and chemistry were tracked by atomic resolution scanning transmission electron microscopy (STEM) imaging and energy dispersive X-ray spectroscopy (EDS). The results of this study can be used as a guideline to control the decoration of solutes at the grain boundary to enable desirable physical and functional properties.