A novel calorimetric approach and analytic method were proposed to characterize the glass transition and fragility of glass-forming systems. Initial characterization of the glass transition temperatures (onset, inflection, and end) was performed by precisely defining these points based on derivative behavior of the total heat flow curve obtained through differential scanning calorimetry (DSC). Geometric representation allowed for consolidation of critical glass transition data into one matrix. This glass transition matrix can be used for automated characterization of the regime, including thermodynamics and kinetics, via programmed computation. Comparison of results to traditional methods revealed excellent agreement with results derived by the novel procedure proposed, and indeed was corroborated by literature values of glass transition temperature, liquid fragility index, and activation energy. The proposed analytic methods establish a significant metrological traceability by development of a robust confidence interval for all targeted measurands, and in so doing provide a highly reproducible and efficient analysis via DSC. K E Y W O R D Scharacterization, calorimetry (or DSC), fragility (or liquid fragility index), glass transition, heat capacity How to cite this article: Mancini M, Sendova M, Mauro JC. Geometric analysis of the calorimetric glass transition and fragility using constant cooling rate cycles.

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Atomic structure dictates the performance of all materials systems; the characteristic of disordered materials is the significance of spatial and temporal fluctuations on composition−structure−property−performance relationships. Glass has a disordered atomic arrangement, which induces localized distributions in physical properties that are conventionally defined by average values. Quantifying these statistical distributions (including variances, fluctuations, and heterogeneities) is necessary to describe the complexity of glassforming systems. Only recently have rigorous theories been developed to predict heterogeneities to manipulate and optimize glass properties. This article provides a comprehensive review of experimental, computational, and theoretical approaches to characterize and demonstrate the effects of short-, medium-, and long-range statistical fluctuations on physical properties (e.g., thermodynamic, kinetic, mechanical, and optical) and processes (e.g., relaxation, crystallization, and phase separation), focusing primarily on commercially relevant oxide glasses. Rigorous investigations of fluctuations enable researchers to improve the fundamental understanding of the chemistry and physics governing glassforming systems and optimize structure−property−performance relationships for next-generation technological applications of glass, including damage-resistant electronic displays, safer pharmaceutical vials to store and transport vaccines, and lower-attenuation fiber optics. We invite the reader to join us in exploring what can be discovered by going beyond the average.

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