Issue 29, 2006

23Na multiple-quantum MASNMR of the perovskites NaNbO3 and NaTaO3

Abstract

The distorted perovskites NaTaO3 and NaNbO3 have been studied using 23Na multiple-quantum (MQ) MAS NMR. NaTaO3 was prepared by high temperature solid state synthesis and the NMR spectra are consistent with the expected room temperature structure of the material (space group Pbnm), with a single crystallographic sodium site. Two samples of NaNbO3 were studied. The first, a commercially available sample which was annealed at 900 °C, showed two crystallographic sodium sites, as expected for the room temperature structure of the material (space group Pbcm). The second sample, prepared by a low temperature hydrothermal method, showed the presence of four sodium sites, two of which match the expected room temperature structure and the second pair, another polymorph of the material (space group P21ma). This is consistent with powder X-ray diffraction data which showed weak extra peaks which can be accounted for by the presence of this second polymorph. Density functional theory (DFT) calculations support our conclusions, and aid assignment of the NMR spectra. Finally, we discuss the measured NMR parameters in relation to other studies of sodium in high coordination sites in the solid state.

Graphical abstract: 23Na multiple-quantum MAS NMR of the perovskites NaNbO3 and NaTaO3

Article information

Article type
Paper
Submitted
28 Mar 2006
Accepted
09 Jun 2006
First published
22 Jun 2006

Phys. Chem. Chem. Phys., 2006,8, 3423-3431

23Na multiple-quantum MAS NMR of the perovskites NaNbO3 and NaTaO3

S. E. Ashbrook, L. Le Pollès, R. Gautier, C. J. Pickard and R. I. Walton, Phys. Chem. Chem. Phys., 2006, 8, 3423 DOI: 10.1039/B604520K

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