Crystal structure of a new high-pressure phase, K0.82Mg1.68(Cr2.84Fe0.84Ti2.11Zr0.08)O12, with one-dimensional tunnels |
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Authors: | Hexiong Yang Jürgen Konzett |
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Institution: | a Department of Mechanical and Materials Engineering, EC, Center for Study of Matter at Extreme Conditions (CeSMEC), Florida International University, University Park, Campus Room VH-140, Miami, FL 33199, USA b Institut für Mineralogie und Petrographie, Universität Innsbruck, Bruno Sander Haus, Innrain 52, A-6020 Innsbruck, Austria |
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Abstract: | The crystal structure of a new complex Ti-Cr oxide phase, K0.82Mg1.68(Cr2.84Fe0.84Ti2.11Zr0.08)O12, synthesized at 13 GPa and 1400 °C, has been determined with single-crystal X-ray diffraction. It has a hexagonal symmetry with the space group P63/m and unit-cell parameters a=9.1763(13) and , , Z=1. The structure is characterized by the hollandite-type double chains of edge-shared M2 octahedra occupied by trivalent and tetravalent cations (Ti+Cr+Fe+Zr); these double chains are linked to one another through shared octahedral apexes to form a framework structure containing two types of tunnels running parallel to the c-axis. One type of tunnels has a hexagonal cross-section and is occupied by large K+, whereas the other has a triangular cross-section and is occupied by Mg2+. The K+ cation is disordered between two crystallographically equivalent (2a) sites in the tunnels and displays a U33 displacement parameter that is significantly greater than U11. The new high-pressure phase reported in this study possesses many structural features similar to those for the hollandite compounds, making it a candidate for the 1-D fast ionic conductors. |
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Keywords: | High-pressure synthesis Complex Ti-Cr oxide Crystal structure of a Ti-Cr oxide |
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