Rietveld refinements using neutron diffraction data have been used to determine the crystal structure of the room temperature polymorph of a new oxide ion conductor, NaBi3V2O10. The cell is isostructural with Pb2Bi2V2O10 and the data refined in spacegroup P1 with cell parameters of a=7.0613(8), b=7.2086(8), c=5.5343(10) Angstrom, alpha=113.328(4), beta=84.4787(14) and gamma=112.249(3)degrees with an R value of 2.19%. The low symmetry of Pb2Bi2V2O10 and NaBi3V2O10 is attributed to structural distortions associated with electron lone pairs on Pb+II and Bi+III. Replacement of Pb+II by Bi+III and Na+I produces a structural phase transition to a higher symmetry polymorph in NaBi3V2O10 at ca. 575 degrees C. ac Impedance measurements show Pb2Bi2V2O10 to be a modest oxide ion conductor with conductivity of ca. 1 mS cm(-1) at 800 degrees C. As a result of the phase transition in NaBi3V2O10 its conductivity is ca. one order of magnitude greater than that of Pb2Bi2V2O10 at 600 degrees C.
|Number of pages||5|
|Journal||Journal of Materials Chemistry|
|Publication status||Published - 1999|