Abstract
The solid– state fuel cell is the most widely adopted energy– generating technology in the world for which different oxide– ion conductors of pervoskite structures have been recently investigated for the application in the intermediate temperature– solid oxide fuel cells (IT–SOFCs). In the present work, samples of single substituted BIMEVOX i.e., BIBIVOX (Bi<sub>2</sub>V<sub>1–<i>x</i></sub>Bi<sub><i>x</i></sub>O<sub>5.5–<i>x</i>/2</sub>) were prepared in the composition range 0 ≥ x ≥ 0.20 using bottom up sol–gel method. XRPD, FT–IR, DTA, SEM, EDS, and AC impedance spectroscopy were used for the investigation of the correlation between the structural phase stability and oxide– ion performance of the BIBIVOX materials. It has been found that orthorhombic, β, and incommensurate tetragonal, γ′–phases were stabilized at room temperature for compositions with <i>x</i>=0.15 and <i>x</i>=0.20, respectively. The enthalpy of β–γ and γ′–γ transition exhibited a general drop with increasing Bi content. The higher value of conductivity of the substituted compound as compared to the parent compound can be attributed to the increased oxygen vacancies generated as a result of cation doping. AC impedance spectroscopy reveals the fact that this ionic conductivity is mainly due to the grain contribution.
Highlights
Conduction in solid electrolytes is mainly due to the migration of whether cations or anions, but generally not both like liquid electrolytes
Bismuth oxide and its solid solutions have been considered to be promising candidates as oxide– ion solid electrolytes, because of their potential to exhibit at intermediate temperatures (300°C–500°C) high oxide– ion conductivities [2,3,4]
All the diffraction patterns for the compositions x < 0.17 appear to be identical to the characteristic β–phase diffraction pattern observed for most of the single substituted BIMEVOXes, indicating no significant polymorphism occurs with the increase of Bi content upto x=0.13
Summary
Conduction in solid electrolytes is mainly due to the migration of whether cations or anions, but generally not both like liquid electrolytes. Bismuth oxide and its solid solutions have been considered to be promising candidates as oxide– ion solid electrolytes, because of their potential to exhibit at intermediate temperatures (300°C–500°C) high oxide– ion conductivities [2,3,4]. BIMEVOXes are divalent substituted systems with general formula Bi2MExV1–xO5.5–x/2, which are produced from a ternary solid solutions of Bi2O3 with V2O5 and usually transition– metal oxides. The parent compound of this family of solid electrolyte, Bi4V2O11, structurally belongs to a layered Aurivillus– type of compounds. These Aurivillus compounds have an inter growth of (Bi2O2)2+ layers and perovskite– like slabs (An–1BnO3n+1)2– that contains oxide– ion vacancies ( ) in the pervoskite– like slabs (VO3.5 0.5)2–. The BIMEVOX family of oxide– ion conductors, based on cation substitution
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