Oxide-ion conduction in anion-deficient double perovskites, Ba2BB′O5.5 (B=Li, Na; B′=Mo, W, Te)
1997; Elsevier BV; Volume: 104; Issue: 3-4 Linguagem: Inglês
10.1016/s0167-2738(97)00424-4
ISSN1872-7689
Autores Tópico(s)Thermal Expansion and Ionic Conductivity
ResumoWe have investigated the oxide-ion conduction of anion-deficient double perovskites of the formula, $Ba_2 BB'O_{5.5} (B = Li, Na; B' = Mo,W, Te)$, in relation to the parent oxides, $Ba_2 BB'O_6 (B = Ca)$. Powder XRD and $^7Li/^{23}$ Na MAS NMR spectra indicate that the oxygen vacancies are not ordered in the $Ba_2 BB'O_{5.5}$ oxides. Anion-deficient oxides show appreciably higher conductivities than the parent stoichiometric oxides. The highest oxide-ion conductivity of $\sim 10^{-2} S/ cm$ at $700^oC$ in this series is exhibited by $Ba_2 NaMoO_{5.5}$. A smooth conductivity transition around $350^oC$ as indicated by a discontinuity in the Arrhenius plots of the molybdenum compounds has been ascribed to a change-over from a two-dimensional to bulk (three-dimensional) oxygen vacancy migration in these oxides.
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