The crystal structure of a new oxide ion conductor NaBi3V2O10 and oxide ion conductivity in Pb2Bi2V2O10
Abstract
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, NaBi
3
V
2
O
10
. The cell is isostructural with Pb
2
Bi
2
V
2
O
10
and the data refined in spacegroup P1 with cell parameters of a = 7.0613(8), b = 7.2086(8), c = 5.5343(10) Å, α = 113.328(4), β = 84.4787(14) and γ = 112.249(3)° with an R value of 2.19%. The low symmetry of Pb
2
Bi
2
V
2
O
10
and NaBi
3
V
2
O
10
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 NaBi
3
V
2
O
10
at ca. 575 °C. ac Impedance measurements show Pb
2
Bi
2
V
2
O
10
to be a modest oxide ion conductor with conductivity of ca. 1 mS cm
–1
at 800 °C. As a result of the phase transition in NaBi
3
V
2
O
10
its conductivity is ca. one order of magnitude greater than that of Pb
2
Bi
2
V
2
O
10
at 600 °C.
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