B.N. Wani

Influence of synthesis route on morphology and conduction behavior of BaCe0.8Y0.2O3−δ

In this article, the role of the preparation route and calcinations temperature on the thermal expansion and conductivity of BaCe0.8Y0.2O3−δ (BCY) has been studied. In particular, the samples were synthesized by means of the solid-state reaction and by a sol–gel route. BCY has been suggested as proton conducting electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Proton conductivity strongly depends on the densification of the material as well as the crystal structure, which is generally influenced by the preparation procedure. It was found that a single phase material could be achieved at 1000xa0°C for the samples prepared through the sol–gel route with ~96% packing density. In case of ceramic route, single phase could be obtained at higher temperatures (1200xa0°C) and does not lead to good density values. The ceramic synthesis produces BCY material in cubic symmetry where as the gel–citrate complexation route leads to homogenous orthorhombic BCY. The conductivity measurements of sample synthesized by two different routes were investigated by means of impedance spectroscopy and electron microscopy. A comparative study of thermal expansion behavior of BCY synthesized by different route was carried out.

Interfacial reaction between ammonium hydrogen fluoride and binary oxides at room temperature

Abstract Interfacial solid state reactions between ammonium hydrogen fluoride and nine different binary oxides, viz., V2O3, V2O5, La2O3, Y2O3, CeO2, Nd2O3, UO2, U3O8, and ThO2 at room temperature are presented. The starting pairs of crystalline reactants, on mere physical contact in different reaction configurations, yield at the interface crystalline products identified as having definite stoichiometry. The role of water in these kinds of reactions is discussed.

Influence of synthesis route on physicochemical properties of nanostructured electrolyte material La0.9Sr0.1Ga0.8Mg0.2O3−δ for IT-SOFCs

Nanosized La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) has been synthesized by both gel-combustion method and solid state reaction method as an electrolyte material for IT-SOFCs. The effect of synthesis route on phase purity of the samples has been studied by X-ray diffraction technique. In the gel-combustion method, perovskite structure was formed at 1,200xa0°C with only trace amount of impurity and has an average crystallite size of 27xa0nm obtained by Scherrer’s equation. In solid state route, phase pure product was obtained only at the calcination temperature of 1,500xa0°C. The characteristics of the samples were also studied using FTIR, TG/DTA, Small angle X-ray scattering, BET surface area, thermal expansion measurements, and electrochemical impedance spectroscopy. The activation energy for oxide ion conduction of LSGM samples derived from Arrhenius plot is ~1.01 and 1.09xa0eV for gel-combustion and ceramic route, respectively. Linear increment of thermal expansion obtained by Dilatometry shows that there is no phase change at higher temperature in the sample. Sintered densities and microstructural features of the samples were also studied. The chemical compatibility of this electrolyte material has been studied with the perovskite oxide-based cathode material La0.6Sr0.4Co0.2Fe0.8O3−δ and NiO.