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Crystals 2018, 8(5), 199; https://doi.org/10.3390/cryst8050199

Structural Phase Transition and Compressibility of CaF2 Nanocrystals under High Pressure

1
Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, National Demonstration Center for Experimental Physics Education, Jilin Normal University, Siping 136000, China
2
State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China
*
Author to whom correspondence should be addressed.
Received: 19 March 2018 / Revised: 26 April 2018 / Accepted: 26 April 2018 / Published: 3 May 2018
(This article belongs to the Special Issue High-Pressure Studies of Crystalline Materials)
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Abstract

The structural phase transition and compressibility of CaF2 nanocrystals with size of 23 nm under high pressure were investigated by synchrotron X-ray diffraction measurement. A pressure-induced fluorite to α-PbCl2-type phase transition starts at 9.5 GPa and completes at 20.2 GPa. The phase-transition pressure is lower than that of 8 nm CaF2 nanocrystals and closer to bulk CaF2. Upon decompression, the fluorite and α-PbCl2-type structure co-exist at the ambient pressure. The bulk modulus B0 of the 23 nm CaF2 nanocrystals for the fluorite and α-PbCl2-type phase are 103(2) and 78(2) GPa, which are both larger than those of the bulk CaF2. The CaF2 nanocrystals exhibit obviously higher incompressibility compare to bulk CaF2. Further analysis demonstrates that the defect effect in our CaF2 nanocrystals plays a dominant role in the structural stability. View Full-Text
Keywords: high pressure; CaF2 nanocrystals; phase transitions; X-ray; bulk modulus high pressure; CaF2 nanocrystals; phase transitions; X-ray; bulk modulus
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Wang, J.; Yang, J.; Hu, T.; Chen, X.; Lang, J.; Wu, X.; Zhang, J.; Zhao, H.; Yang, J.; Cui, Q. Structural Phase Transition and Compressibility of CaF2 Nanocrystals under High Pressure. Crystals 2018, 8, 199.

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