An Innovative Measurement Protocol for Determining the True Glass Transition Temperature of Chalcogenide Glasses by Differential Scanning Calorimetry

The glass transition temperature, Tg, is one of the most important physical attributes of a glass. The value of Tg often defines how a glass is made and used and dramatically impacts the electrical, mechanical, optical, and transport properties of the material. Despite its importance, the manner in which the thermal equilibrium temperature value for Tg is defined and measured in the chalcogenide glass community varies widely among researchers and practitioners leading to confusion about the term and misrepresentation of the property. Unique to this glass community, the measurement instrument of choice is the Differential Scanning Calorimeter. Countless variations in practice, coupled with incorrect equations which have been passed down unchallenged for more than 55 years, have yielded hundreds of peer-reviewed research papers and dozens of undergraduate and graduate theses. We review representative research and apply equations recently corrected by members of our team to reveal how a novel mathematical extrapolation technique to a "zero" heating rate limit provides an innovative analytical technique which will determine what we call the "true" glass transition temperature Tg(0) of a chalcogenide glass composition at isothermal equilibrium. Received: 18 November 2024 | Revised: 3 January 2025 | Accepted: 13 February 2025 Conflicts of Interest The authors declare that they have no conflicts of interest to this work. Data Availability Statement Data are available from the corresponding author upon reasonable request. Author Contribution Statement Thomas J. Loretz: Conceptualization, Methodology, Software, Validation, Formal analysis, Data curation, Writing – original draft, Writing – review & editing, Visualization, Project administration. Rashi Sharma: Investigation, Resources, Writing – review & editing. Anna Zachariou: Investigation, Resources. Richard A. Loretz: Validation, Formal analysis, Data curation, Writing – review & editing, Visualization. Myungkoo Kang: Investigation, Writing – review & editing. Kathleen A. Richardson: Conceptualization, Validation, Writing – review & editing, Supervision, Project administration, Funding acquisition.