Crystal-to-stripe reordering of sodium ions in NaxCoO2 (x>=0.75)

Abstract

The sodium reordering in NaxCoO2 in the vicinity of room temperature is rationalized at high x in terms of phase transitions between square and striped phases. A striking hexagon-of-hexagons diffraction pattern observed for x=0.78 can be reproduced using coexisting square and striped phases that are related by simple shear deformations. All compositions exhibit a partial melting transition to a disordered stripe phase just below room temperature, which alters the topology of the electrical conduction pathways.

arXiv commentPublished in Phys. Rev. B

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• Na-ion dynamics in Quasi-1D compound NaV2O4
• Novel electronic states realized by the interplay between Li diffusion and Co${}^{3+}$$/$Co${}^{4+}$ charge ordering in Li${}_{\mathrm{x}}$CoO${}_2$
• The Duel of Magnetic Interactions & Structural Instabilities: Itinerant Frustration in the Triangular Lattice Compound LiCrSe${}_2$
• Interplay between magnetism and sodium vacancy ordering in NaxCoO2
• Transition from a phase-segregated state to single-phase incommensurate sodium ordering in Na_xCoO_2 with x \approx 0.53
• Divacancy superstructures in thermoelectric calcium-doped sodium cobaltate
• Sodium ion ordering of Na0.77CoO2 under competing multi-vacancy cluster, superlattice and domain formation