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Primary (α) structural relaxation is known to influence the nucleation behavior in glasses and it has recently been proposed to account for the so-called classical nucleation theory "breakdown" in oxide glasses around the glass transition temperature. However, it is unclear whether secondary (β -) relaxation, predominant at lower temperatures, also plays a role in promoting crystallization. Here, we study the correlation between crystallization kinetics and β -relaxation of three types of oxide glasses with distinct chemical bonds by subjecting the glasses to low-temperature annealing. We find that the activation energy of crystallization (E a) exhibits an exponential decay with increasing annealing duration for all studied glasses. Such a decrease in E a is found to be associated with the structural rearrangements in the glasses, especially showing a negative correlation with the enhanced atomistic interplays around modifying cations. Our findings thus point to a universal linkage between β -relaxation and nucleation kinetics in oxide network glasses. [Display omitted] [ABSTRACT FROM AUTHOR]

Although remarkable development of titanate‐based glasses has been achieved, challenge remains to elucidate the correlation between structure and glass‐forming properties in these systems due to their complex structure that is inconsistent with the classic Zachariasen's model. In this work, we aim to correlate the structural evolution of titanate melts to their glass‐forming ability (GFA). The prototypical material barium dititanate (BaTi2O5, BT2) melts with different GFA were rendered by controlled melting atmospheres, and the corresponding structural changes were determined using in situ high‐energy synchrotron X‐ray diffraction combined with empirical potential structure refinement and ab initio molecular dynamics. The results show that BT2 melt in reducing atmosphere shows poor GFA but that in oxidizing atmosphere presents good GFA. Structural analysis demonstrates the mean coordination number of [TiOm] polyhedra is analogous in the melt under two different atmospheres but an enhanced heterogeneous cations aggregation takes place in the melt under reducing atmosphere, which is closely related to oxygen‐deficiencies. Furthermore, we reveal that the enhanced heterogeneous cations aggregation promotes crystallization (and therefore hinders glass formation) through disordering the distribution of [TiOm] and [BaOn] polyhedra, changing the connectivity between these polyhedra, creating more crystal‐like Ti‐Ti clusters, and decreasing topological disorder of BT2 melt. Our work provides a new viewpoint to understand the GFA of titanates melt from structural heterogeneity beyond the previous perspectives that only focus on [TiOm] polyhedra. [ABSTRACT FROM AUTHOR]

Annealed titanate glasses are important candidate materials for high-performance electronic components, but their structural response to temperature-induced properties upon thermal annealing remains elusive. Here, using high-energy synchrotron X-ray scattering, high-temperature Raman spectroscopy, and empirical potential structure refinement simulation, we track the structural evolution in situ of a barium dititanate (BaTi 2 O 5) glass upon annealing around and below the glass transition temperature. We find that the network structure is intrinsically floppy, as the network units ([TiO m ] polyhedra) themselves and their topological packing can be easily modulated by annealing temperature. The floppy nature of the glassy titanate network challenges the currently well-cognized Rigid-Unit Mode model explaining temperature-driven structural reorganization of prototypical network glasses (e.g., silicate/borate glasses). As temperature increases, the floppy network of BaTi 2 O 5 glass undergoes a non-monotonic, two-stage network rearrangement. After cooling back to room temperature, the distortion of network units is found recoverable whereas the change of network connectivity in the intermedium-range order is irreversible. Simulation ensembles further show the irreversible connectivity change can be ascribed to the local development of crystal-like cationic motifs, which in turn induce excess enthalpy relaxation. Our findings provide an atomic-scale perspective on temperature-dependent structural and enthalpy relaxation of a model titanate glass upon annealing, which are crucial for understanding thermal-related changes in the properties of titanate glasses. [Display omitted] [ABSTRACT FROM AUTHOR]