Rietveld refinement results on three nonstoichiometric monoclinic NASICONs
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The results of three powder Rietveld refinements of monoclinic NASICONs, prepared by different methods, are examined. Neutron TOF data were collected on two samples: a sol-gel prepared NASICON was found to have the formula Na3Zr1.93Si2PO11.86 and a reheated commercially available NASICON a formula of Na3.17Zr1.93Si1.9P1.1O12. Following our neutron study on a nonstoichiometric hydrothermally prepared NASICON we prepared the same nonstoichiometric phase by sol-gel methods and X-ray Rietveld analysis yielded the formula Na3.2Zr1.68Si1.84P1.16O11.54. These stoichiometries can be represented by the general formula Na1+4y+xZr2-y-zSixO12-2z where z represents the ZrO2 mole deficiency and y the amount of Zr4+ vacancies compensated by 4Na+. These differences in stoichiometry are accompanied by structural differences such as Si/P segregation and variations in cavity occupancy by Na+. It is proposed that the method of preparation is largely responsible for the observed differences. © 1986.
author list (cited authors)
Rudolf, P. R., Clearfield, A., & Jorgensen, J. D.