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High-Pressure High-Temperature Exploration of Phase Boundaries Using Raman Spectroscopy

Abstract

Metastability of states can provide interesting properties that may not be readily accessible in a material’s ground state. Many materials show high levels of polymorphism, indicating a rich energy landscape and a potential for metastable states. Melt crystallization techniques provide a potential route to these states. We use a resistively heated diamond anvil cell (DAC) with fine control of a system’s pressure and temperature to explore these systems. Raman spectroscopy is used to track subtle structural changes across phase boundaries. Organic systems, such as glycine and aspirin, were our initial interest due to their high polymorphism and reported low melting temperatures; however, complications with these systems ultimately showed that they are not ideal candidates for this technique. Metallic systems with allowed Raman modes are better samples for this method. We successfully map the phase stability of β-tin under high pressure and temperature conditions using Raman spectroscopy

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