Phase segregation in NaxCoO2 for large Na contents
T. A. Platova+*, I. R. Mukhamedshin+*, A. V. Dooglav+, H. Alloul*
+Physics Department, Kazan State University, 420008 Kazan, Russia
*Laboratoire de Physique des Solides, UMR 8502, Université Paris-Sud, 91405 Orsay, France
Abstract
We have investigated a set of sodium cobaltates (NaxCoO2)
samples with various sodium content 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.