| Autor: |
Hu, Yancheng, Ye, Yu, Liu, Dan, Wang, Zhengrong, Zhu, Xi, Wang, Sha, Miao, Yunfan, Wu, Zhen |
| Zdroj: |
The Journal of Physical Chemistry - Part C; April 2024, Vol. 128 Issue: 14 p6138-6148, 11p |
| Abstrakt: |
Calcium carbonate (CaCO3) is an important carbon host on Earth, playing a key role in the global carbon cycle. Barium-bearing carbonate has unique properties that demand a systematic study. Nine BaxCa1–xCO3(0.10 ≤ x≤ 0.89) solid solutions were synthesized at 2.5 GPa (gigapascal) and 1200 °C. Single-crystal X-ray diffraction analyses indicate that the phases with x≤ 0.19 and x≥ 0.27 form in the symmetry of R3̅cand R3̅m, respectively. The aand caxes and average Ca(Ba)–O bond length increase gradually with the increasing Ba2+concentration. The replacement of Ca2+by Ba2+helps stabilize the aplanarity and disordered orientations of CO3groups down to ambient condition. X-ray photoelectron spectroscopy was measured on these synthetic samples, and their structural environments of atoms are similar to those in pure calcite. The Raman- and IR-active modes generally show a red-shift with the incorporation of Ba2+, without any significant difference between the ordered and disordered structures. The R3̅mphases transform to the aragonite-type structure around 1000 K. This study provides useful structural information for both bioinspired materials and carbonate minerals, with implications to the phase transitions in carbonates at high P–Tconditions in Earth’s interior. |
| Databáze: |
Supplemental Index |
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