Slow coarsening of tetragonal zirconia nanocrystals in a phase-separated sodium borosilicate glass

• Published in: Journal of non-crystalline solids 2023-04, Vol.606, p.122206, Article 122206
• Main Authors: Fritzsche, J.O., Rüdinger, B., Deubener, J.
• Format: Article
• Language: English
• Subjects: Borosilicate glass; Coarsening; Confinement; Phase separation; Tetragonal zirconia
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2023.122206

•A Zr4+-containing borosilicate glass was prepared by melt quenching.•Phase separation with dissolution of Zr4+ in both boron- and silica-rich domains.•Crystallisation of tetragonal ZrO2 in the boron-rich domains.•Slow coarsening of tetragonal ZrO2 with a power law exponent ∼1/6.•Transformation of tetragonal to monoclinic ZrO2 near predicted crystal size limit. A Zr4+-containing sodium borosilicate glass (ZNBS) and a zirconium-free reference glass (NBS) were prepared by melt quenching. Thermal analysis revealed two glass transitions, indicating that both glasses exhibit phase separation into boron- and silica-rich domain structures already after quenching to room temperature. Electron micrographs showed that annealing of NBS and ZNBS glasses initiated the coarsening of these domains and the precipitation of metastable t-ZrO2 in the boron-rich matrix of the ZNBS glass. The coarsening kinetics of the silica-rich domains followed the theoretical predictions (power law exponent = 1/3), while the coarsening of the t-ZrO2 crystallites was much slower. The time evolution of the average size of t-ZrO2 nanocrystallites from small angle X-ray scattering (SAXS) and high-temperature X-ray diffraction (HTXRD) experiments revealed a coarsening exponent of ∼1/6. This slow coarsening of t-ZrO2 is assumed to be confined by the domain structure of the primary phase separation.