Single crystal growth, characterization and high-pressure Raman spectroscopy of impurity-free magnesite

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Marco E. Ciriotti
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Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Single crystal growth, characterization and high-pressure Raman spectroscopy of impurity-free magnesite

Messaggio da Marco E. Ciriotti » mer 23 mag, 2018 16:30

Referenza:
▪ Liang, W., Li, Z., Yin, Y., Li, R., Chen, L., He, Yu, Dong, H., Dai, L., Li, H. (2018): Single crystal growth, characterization and high-pressure Raman spectroscopy of impurity-free magnesite (MgCO3). Physics and Chemistry of Minerals, 45, 423-434.

Abstract:
The understanding of the physical and chemical properties of magnesite (MgCO3) under deep-mantle conditions is highly important to capture the essence of deep-carbon storage in Earth’s interior. To develop standard rating scales, the impurity-free magnesite single crystal, paying particular attention to the case of avoiding adverse impacts of Ca2+, Fe2+, and Mn2+ impurities in natural magnesite, is undoubtedly necessary for all research of magnesite, including crystalline structural phase transitions, anisotropic elasticity and conductivity, and equation of state (EoS). Thus, a high-quality single crystal of impurity-free magnesite was grown successfully for the first time using the self-flux method under high pressure–temperature conditions. The size of the magnesite single crystal, observed in a plane-polarized microscope, exceeds 200 μm, and the crystal exhibits a rhombohedral structure to cleave along the (101) plane. In addition, its composition of Mg0.999 ± 0.001CO3 was quantified through electron probing analysis. The structural property was investigated by means of single crystal X-ray diffraction and the unit cell dimensions obtained in the rhombohedral symmetry of the Rc space group are a = 4.6255 (3) and c = 14.987 (2), and the final R = 0.0243 for 718 reflections. High-pressure Raman spectroscopy of the magnesite single crystal was performed up to 27 GPa at ambient temperature. All Raman active bands, ν i, without any splitting increased almost linearly with increasing pressure. In combination with the high-pressure Raman results dνidP and the bulk modulus K T (103 GPa) reported from magnesite EoS studies, the mode Grüneisen parameters (1.49, 1.40, 0.26, and 0.27) of each vibration (T, L, ν 4, and ν 1) were calculated.
Marco E. Ciriotti

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