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Open AccessArticle

The Phase Transition and Dehydration in Epsomite under High Temperature and High Pressure

1
Key Laboratory of High-Temperature and High-Pressure Study of the Earth’s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guizhou 550081, Guiyang, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
*
Author to whom correspondence should be addressed.
Crystals 2020, 10(2), 75; https://doi.org/10.3390/cryst10020075
Received: 15 January 2020 / Revised: 27 January 2020 / Accepted: 28 January 2020 / Published: 30 January 2020
(This article belongs to the Special Issue Pressure-Induced Phase Transformations)
The phase stability of epsomite under a high temperature and high pressure were explored through Raman spectroscopy and electrical conductivity measurements in a diamond anvil cell up to ~623 K and ~12.8 GPa. Our results verified that the epsomite underwent a pressure-induced phase transition at ~5.1 GPa and room temperature, which was well characterized by the change in the pressure dependence of Raman vibrational modes and electrical conductivity. The dehydration process of the epsomite under high pressure was monitored by the variation in the sulfate tetrahedra and hydroxyl modes. At a representative pressure point of ~1.3 GPa, it was found the epsomite (MgSO4·7H2O) started to dehydrate at ~343 K, by forming hexahydrite (MgSO4·6H2O), and then further transformed into magnesium sulfate trihydrate (MgSO4·3H2O) and anhydrous magnesium sulfate (MgSO4) at higher temperatures of 373 and 473 K, respectively. Furthermore, the established P-T phase diagram revealed a positive relationship between the dehydration temperature and the pressure for epsomite. View Full-Text
Keywords: epsomite; phase transition; dehydration reaction; Raman spectra; electrical conductivity; high pressure epsomite; phase transition; dehydration reaction; Raman spectra; electrical conductivity; high pressure
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MDPI and ACS Style

Yang, L.; Dai, L.; Li, H.; Hu, H.; Hong, M.; Zhang, X. The Phase Transition and Dehydration in Epsomite under High Temperature and High Pressure. Crystals 2020, 10, 75. https://doi.org/10.3390/cryst10020075

AMA Style

Yang L, Dai L, Li H, Hu H, Hong M, Zhang X. The Phase Transition and Dehydration in Epsomite under High Temperature and High Pressure. Crystals. 2020; 10(2):75. https://doi.org/10.3390/cryst10020075

Chicago/Turabian Style

Yang, Linfei; Dai, Lidong; Li, Heping; Hu, Haiying; Hong, Meiling; Zhang, Xinyu. 2020. "The Phase Transition and Dehydration in Epsomite under High Temperature and High Pressure" Crystals 10, no. 2: 75. https://doi.org/10.3390/cryst10020075

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