Structural transition in NaxCoO2 with x near 0.75 due to Na rearrangement
Journal
Physical Review B - Condensed Matter and Materials Physics
Journal Volume
70
Journal Issue
13
Pages
134115-1-134115-6
Date Issued
2004
Author(s)
Abstract
We report neutron powder diffraction measurements on a series of Na xCoO2 samples with x near 0.75 which were prepared under different synthesis conditions. Two different crystal structures for the samples are observed at room temperature. The two structures belong to the space group P63/mmc and differ primarily by a shift of a large fraction of the Na ions from a high-symmetry position to a lower-symmetry position. Close inspection of the refinement parameters indicates that the presence of either structure depends sensitively on the Na content x, with x ≃ 0.75 as the critical concentration separating the two phases. By raising the temperature to around T ≃ 323 K, the high-symmetry structure can be converted to the lower-symmetry structure. The transition is reversible, but there is significant hysteresis. We discuss the effects of this structural transition on the bulk magnetic and transport properties.
Type
journal article