Abstract
Samples of the system Bi4Ag x V2– x O11–(2 x )–δ, 0.05 ≤ x ≤ 0.30 abbreviated by the acronym, BIAGVOX were readily synthesized by the standard solid state reaction. The composition and temperature dependence of polymorphism and of oxide ion performance were investigated using differential thermal analysis, and variable temperature X-ray powder diffraction and AC impedance spectroscopy. The partial substitution of larger Ag+ ion for V5+ in the parent compound has led to the occurrence of two phase transitions; β → γ and γ′ → γ for compositions x ≤ 0.15 and x ≥ 0.20, respectively. δ-Hexagonal phase was also formed within the stability region of γ′ → γ transition at elevated temperatures. The temperature dependence of conductivity was typically influenced by these transitions. However, the oxide ion performance of γ′-phase increased with increasing composition at lower temperatures, while that of γ-phase showed a maximum at higher temperatures for x = 0.20.
Acknowledgements
This work was financially supported by Universities Grants Commission (UGC), Grant no. 39-798/2010 (SR), New Delhi, India. The authors are also grateful to Taiz University – Republic of Yemen for the kind assistance.