The high-pressure behavior of monovalent-cation-exchanged chabazites was investigated by means of in situ synchrotron X-ray powder diffraction with a diamond-anvil cell, and using water as penetrating pressure-transmitting medium, up to 5.5 GPa at room temperature. In all cases, except for Na-containing chabazites, a phase transition from the original rhombohedral (R3m) to triclinic symmetry (likely P1) was observed in the range between 3.0 GPa and 5.0 GPa. The phase transition is accompanied by an abrupt decrease of the unit-cell volume by up to 10%. Evidence of pressure-induced hydration (PIH), i.e., P-induced penetration of H2O molecules through the zeolitic cavities, was observed, as reflected by the incompressibility of the cation-exchanged chabazites, which is governed by the distribution of the extra-framework cations. The reversibility of the PIH and P-induced phase transitions in the high-pressure behavior of the cation-exchanged chabazites are discussed in the context of the role played by the chemical nature and bonding configuration of the extra-framework cations, along with that of the H2O content at room conditions.
Bibliographical noteFunding Information:
This work was supported by the Global Research Laboratory (NRF-2009-00408) and National Research Laboratory (NRF-2015R1A2A1A01007227) programs of the Korean Ministry of Science, ICT and Planning (MSIP). We also thank the supports by NRF-2016K1A4A3914691 and NRF-2016K1A3A7A09005244 grants. Experiments using X-ray synchrotron radiation were supported by the Collaborative Access Program of SSRL. Two anonymous reviewers are thanked for their suggestions.
© 2018 Walter de Gruyter GmbH, Berlin/Boston 2018.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology