STRUCTURAL CHARACTERIZATION OF NA2ZRO3

A combination of X-ray and electron diffraction, electron microscopy a nd solid-state nuclear magnetic resonance (NMR) has been used to eluci date the structure and the ordering of Na2ZrO3. The diffraction data c onfirm a monoclinic crystal structure. A sample prepared by a conventi onal solid-state reaction of the components is shown by both X-ray dif fraction and electron microscope imaging to have an extremely high con centration of planar defects associated with stacking disorder of the planes along the c-axis. The incidence of these defects is significant ly reduced in a sample recrystallised from a bismuth oxide flux. NMR i ndicates that the local coordinations are well defined in both samples but with some sharpening of the spectra from the recrystallised sampl e indicative of the increase of long-range order. The Na-23 magic angl e spinning (MAS) NMR spectra clearly show three distinct sites with wi dely differing quadrupolar interaction parameters that can be related to the known site symmetries. Two distinct oxygen resonances are obser ved in the MAS NMR spectrum from an O-17-enriched sample while the sta tic Zr-91 NMR spectrum can be simulated with one set of interaction pa rameters.