Phase segregation in NaxCoO2 for large Na contents

Abstract

We have investigated a set of sodium cobaltates (NaxCoO2) samples with various sodium content (0.67 \le x \le 0.75) using Nuclear Quadrupole Resonance (NQR). The four different stable phases and an intermediate one have been recognized. The NQR spectra of 59Co allowed us to clearly differentiate the pure phase samples which could be easily distinguished from multi-phase samples. Moreover, we have found that keeping samples at room temperature in contact with humid air leads to destruction of the phase purity and loss of sodium content. The high sodium content sample evolves progressively into a mixture of the detected stable phases until it reaches the x=2/3 composition which appears to be the most stable phase in this part of phase diagram.

5 pages, 4 figures

References in corpus (10)

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• Investigation of the Spin Density Wave in NaxCoO2

Cited by in corpus (7)

• 59Co NMR evidence for charge and orbital order in the kagome like structure of Na2/3CoO2
• Na order and Co charge disproportionation in Na${}_x$CoO${}_2$
• 23Na NMR study of sodium order in NaxCoO2 with 22K Neel temperature
• Evolution of Co charge disproportionation with Na order in Na${}_x$CoO${}_2$
• Dynamic characterization of crystalline and glass phases of deuterated 1,1,2,2 Tetrachloroethane
• Synthesis of sodium cobaltate Na${}_x$CoO${}_2$ single crystals with controlled Na ordering
• Exploring the possibility of enhancing the figure-of-merit ( $>$ 2) of Na${}_{0.74}$CoO${}_2$: A combined experimental and theoretical study