Stoichiometry, structure and conductivity of Nasicon
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The crystal structures of two near stoichiometric NASICONS were determined from powder neutron diffraction data. The compound prepared by Hong's solid state reaction had a composition Na3.17Zr1.93Si1.9P1.1O12 and a sol-gel preparation heated at 1080°C gave Na3Zr1.93Si2PO11.86. These compositions, obtained from refinement of the occupancy factors, were found to agree with elemental analysis carried out by X-ray fluorescence. The foregoing compositions are considerably different from that of a NASICON obtained by a hydrothermal route, Na3.2Zr1.68Si1.84P1.16O11.54, and their unit cell parameters are somewhat larger. This difference results from the incorporation of approximately 0.32 moles of Na+ in the Zr4+ sites for the hydrothermal preparation. Solid state MAS NMR data are presented to support this finding, and in one sample, trapped electrons were detected. The hypothesis is proposed that the exact stoichiometry of NASICON cannot be represented by a simple solid solution series, but rather, depends on the method of preparation. © 1986.
author list (cited authors)
Clearfield, A., Subramanian, M. A., Rudolf, P. R., & Moini, A.