Regensburg 2022 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 30: Liquid and Amorphous Metals

MM 30.9: Vortrag

Donnerstag, 8. September 2022, 12:30–12:45, H46

Anomalous Liquids on a New Landscape: from Water to Phase-Change Materials — •Shuai Wei — Aarhus University, Aarhus, Denmark

A liquid that is cooled below its melting temperature, referred to as a supercooled liquid, can solidify into an amorphous rigid state (i.e., glass), if cooling is fast enough and crystallization is avoided. The phenomenology of supercooled liquids has been in general established. However, there are pronounced exceptions (e.g., water) which do not fall into the class of "normal" liquids but exhibit a transition behavior in their liquid states. The latest advances connect the unusual aspect of liquids to the properties of Phase-Change Materials (PCMs) that are the basis for non-volatile memory and neuromorphic technologies. Here we demonstrate that the "water-like" liquid anomalies exist in many alloys based on group-IV, V, VI elements including technologically important PCMs. Heat capacity, density, and thermal expansivity maxima were observed in the (supercooled) liquid states of those alloys. Structural changes were monitored using in-situ X-ray scattering and femtosecond X-ray diffractions. Dynamic properties were characterized by quasi-elastic neutrons scattering. Their anomalous behaviors can be rationalized in terms of liquid-liquid (metal-semiconductor, and fragile-strong) transitions. These transition behaviors have important implications for understanding the unusual phase switching behaviors in PCMs, in which amorphous phase can crystallize rapidly within tens of nanoseconds at an elevated temperature, while it retains excellent amorphous stability for 10 years at room temperature.