Transformation of natural pollucite into hexacelsian under high pressure and temperature

Wooseung Choi, Jinhyuk Choi, Huijeong Hwang, Yongjae Lee

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Synchrotron X-ray powder diffraction experiments were performed on natural pollucite to observe its transition into hexacelsian-like phase at high pressure and temperature conditions under water pressure medium. When heated to 100 °C at 1.3(1) GPa, the natural cubic pollucite, (Cs, Na)16Al16Si16O96 (Ia3 ¯ d), transformed to its triclinic phase (P1 ¯) with discontinuous unit cell volume contraction by ca. 4.4%. After further compression to 4.1(1) GPa and heating up to 250 °C, a new hexagonal phase with a hexacelsian framework, Cs1.28(1)Na0.44(1)Al1.72(1)Si6.28(1)O16 (P63/mcm, (Cs, Na)-HEX), formed with unit cell volume contraction by ca. 6.1% based on 96 oxygen atoms of the framework (Of). The structural model of the newly formed hexacelsian-like phase, (Cs, Na)-HEX, was refined by the Rietveld method to show the disordered distribution of cesium and sodium cations between the double six-membered rings (D6R). Further details of the (Cs, Na)-HEX model are compared to those of the natural Ba-hexacelsian (Ba-HEX) and synthetic Cs-hexacelsian (Cs-HEX).

Original languageEnglish
Article number15
JournalPhysics and Chemistry of Minerals
Issue number5
Publication statusPublished - 2022 May

Bibliographical note

Funding Information:
The X-ray experiment was performed at the beamline 10C at PLS-II funded by the Korean Ministry of Science and ICT (MSIT). This work was supported by the Leader Researcher program (NRF‐2018R1A3B1052042) of MSIT.

Publisher Copyright:
© 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Geochemistry and Petrology


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