Topotactic, pressure-driven, diffusion-less phasetransition of layered CsCoO2to a stuffedcristobalite-type configuration
- CsCoO2, featuring a two-dimensional layered architecture of edge- and vertex-linked CoO4tetrahedra, is subjected to a temperature-driven reversible second-order phase transformation at 100 K, which corresponds to a structuralrelaxation with concurrent tilting and breathing modes of edge-sharing CoO4tetrahedra. In the present investigation, it was found that pressure induces a phase transition, which encompasses a dramatic change in the connectivity ofthe tetrahedra. At 923 K and 2 GPa, beta-CsCoO2 undergoes a first-order phasetransition to a new quenchable high-pressure polymorph,alpha-CsCoO2. It is built up of a three-dimensional cristobalite-type network of vertex-sharing CoO4 tetrahedra. According to a Rietveld refinement of high-resolution powderdiffraction data, the new high-pressure polymorph gamma-CsCoO2 crystallizes in the tetragonal space groupI41/amd:2 (Z= 4) with the lattice constants a= 5.8711 (1) and c= 8.3214 (2) A, corresponding to a shrinkage in volume by 5.7% comparedCsCoO2, featuring a two-dimensional layered architecture of edge- and vertex-linked CoO4tetrahedra, is subjected to a temperature-driven reversible second-order phase transformation at 100 K, which corresponds to a structuralrelaxation with concurrent tilting and breathing modes of edge-sharing CoO4tetrahedra. In the present investigation, it was found that pressure induces a phase transition, which encompasses a dramatic change in the connectivity ofthe tetrahedra. At 923 K and 2 GPa, beta-CsCoO2 undergoes a first-order phasetransition to a new quenchable high-pressure polymorph,alpha-CsCoO2. It is built up of a three-dimensional cristobalite-type network of vertex-sharing CoO4 tetrahedra. According to a Rietveld refinement of high-resolution powderdiffraction data, the new high-pressure polymorph gamma-CsCoO2 crystallizes in the tetragonal space groupI41/amd:2 (Z= 4) with the lattice constants a= 5.8711 (1) and c= 8.3214 (2) A, corresponding to a shrinkage in volume by 5.7% compared with the ambient-temperature and atmospheric pressure-CsCoO2polymorph.The pressure-induced transition (beta>gamma) is reversible;-CsCoO2 stays metastable under ambient conditions, but transforms back to the-CsCoO2structure upon heating to 573 K. The transformation pathway revealed isremarkable in that it is topotactic, as is demonstrated through a clean displacive transformation track between the two phases that employs the symmetry oftheir common subgroupPb21a(alternative setting of space group No. 29 that matches the conventional-phase cell).…
Autor*innen: | Naveed Zafar Ali, B. J. Campbell, M. Jansen |
---|---|
Dokumenttyp: | Zeitschriftenartikel |
Veröffentlichungsform: | Verlagsliteratur |
Sprache: | Englisch |
Titel des übergeordneten Werkes (Englisch): | Acta crystallographica section b-structural science crystal engineering and materials |
Jahr der Erstveröffentlichung: | 2019 |
Organisationseinheit der BAM: | 6 Materialchemie |
6 Materialchemie / 6.3 Strukturanalytik | |
Verlag: | International Union of Crystallography |
Jahrgang/Band: | 75 |
Ausgabe/Heft: | 4 |
Erste Seite: | 704 |
Letzte Seite: | 710 |
DDC-Klassifikation: | Naturwissenschaften und Mathematik / Chemie / Analytische Chemie |
Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten | |
Freie Schlagwörter: | Cristobalite frameworks; Oxocobaltates; Structures under extreme conditions; Topotactic phase transitions; Transformation pathways |
Themenfelder/Aktivitätsfelder der BAM: | Chemie und Prozesstechnik |
Material | |
DOI: | 10.1107/S2052520619008436 |
ISSN: | 2052-5206 |
Verfügbarkeit des Dokuments: | Datei im Netzwerk der BAM verfügbar ("Closed Access") |
Datum der Freischaltung: | 29.08.2019 |
Referierte Publikation: | Ja |
Datum der Eintragung als referierte Publikation: | 29.08.2019 |