College Park, Maryland      June 6 - 10 , 2004

ACNS Home Meeting Announcement Committees and Contacts Registration Abstract Submission Travel Reimbursement Dates to Remember

W2-C3 (2:15 PM): Crystal Structure of the Sodium Cobaltate Deuterate Superconductor Na_xCoO₂ 4xD₂O (x=1/3)

M. Avdeev, J.D. Jorgensen, D.G. Hinks, J.C. Burley, S. Short, P.W. Barnes (Materials Science Division, Argonne National Laboratory)

Neutron and x-ray powder diffraction have been used to investigate the crystal structures of a sample of the newly-discovered superconducting sodium cobaltate deuterate compound with composition Na_0.31(3)CoO₂*1.25(2)D₂O and its anhydrous parent compound Na_0.61(1)CoO₂. The deuterate superconducting compound is formed by coordinating four D₂O molecules (two above and two below) to each Na ion in a way that gives Na-O distances nearly equal to those in the parent compound. One deuteron of the D₂O molecule is hydrogen bonded to an oxygen atom in the CoO₂ plane and the oxygen atom and the second deuteron of each D₂O molecule lie approximately in a plane between the Na layer and the CoO₂ layers. This coordination of Na by four D₂O molecules leads to ordering of the Na ions and D₂O molecules. The sample studied here, which has T_c=4.5 K, has a refined composition of Na_0.31(3)CoO₂*1.25(2)d2\nO, in agreement with the expected 1:4 ratio of Na to D₂O. The crystal structure of the intermediate monolayer hydrate is discussed.

Back to the Program