کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1296303 | 973771 | 2011 | 8 صفحه PDF | دانلود رایگان |
Structure and electrical behaviour are reported for the system Bi1-xTaxO1.5 + x (0.167 ≤ x ≤ 0.250). In the compositional range 0.200 < x ≤ 0.250 an incommensurately modulated pseudo-cubic phase (type II) is observed, with the appearance of a larger pseudo-cubic phase in the region 0.167 ≤ x ≤ 0.200. Structural analysis of the type II phases by neutron diffraction reveals subtle changes in the oxide ion distribution with temperature, associated with changes in the incommensurate modulation parameter. Analysis of the defect structure of the type II phase reveals chains of tantalate octahedra as a likely structural motif. It is proposed that these chains facilitate an electronic contribution to total conductivity at low temperatures through electron hopping along the chains. Changes in oxide ion vacancy ordering may explain the observed non-linear behaviour in the thermal expansion of lattice parameter and Arrhenius plots of total conductivity.
► Oxide ion conductors Bi1-xTaxO1.5 + x (0.167 ≤ x ≤ 0.250).
► Two pseudo-cubic phases observed.
► Chains of tantalate octahedra in type II incommensurate phase.
► Oxide ion distribution correlated to electrical behaviour and thermal expansion.
Journal: Solid State Ionics - Volume 202, Issue 1, 2 November 2011, Pages 22–29