Sol–gel synthesis, X-ray photoelectron spectroscopy and electrical conductivity of Co-doped (La, Sr)(Ga, Mg)O3−δ perovskites

La0.8Sr0.2Ga0.8Mg0.2−xCoxO3−δ (LSGMC) powders containing different amounts of Co (x = 0.05 and 0.085) were prepared by a citrate sol–gel method. The powders were used to prepare highly phase-pure LSGMC sintered pellets with controlled composition and fractional densities larger than 95%. For the first time, LSGMC materials were subjected to X-ray photoelectron spectroscopy (XPS) characterization. XPS data confirmed the presence of the dopants in the material and allowed to identify two different chemical states for Sr2+ and oxygen, both related to the oxygen-deficient perovskite structure of LSGMC. The conductivity of LSGMC sintered pellets containing different amounts of Co ions in the B sites of the perovskite lattice was assessed by electrochemical impedance spectroscopy (EIS) in the 250–750 °C temperature range. Conductivity values and apparent activation energies were in good agreement with previously published data referring to materials with same composition, but prepared by solid-state route. Therefore, the physicochemical and electrochemical characterization clearly demonstrated the ability of sol–gel methods to produce high-purity Co-doped LSGM perovskites, which represent promising solid electrolytes for intermediate-temperature SOFCs

Ion exchange effect on asymmetric dioxins adsorption onto FAU-type X-zeolites

International audienceThe effect of trivalent cation exchange on fully dehydrated (activated) FAU-type X-zeolites with respect to the adsorption of the sterically biggest, asymmetric dioxin-molecules (1,2,3,4 TeCDD) in iso-octane solvent was investigated. FAU 13X Na zeolites were selected due to their pore openings, close to the diameter of the 2,3-DCDD (0.74 nm) as well as their high adsorption affinity for this dioxin molecule. This zeolite also adsorbed 1,4 DCDD, but with significantly lower affinity.With the aim to eventually liberate the channel's access for the sterically biggest dioxin molecule 1,2,3,4 TeCDD, Na+ cations were replaced by trivalent cation species Y3+, Ce3+ and La3+. Symmetric dioxins were not tested in this study due to their high toxicity.Analyses performed indicate that cation exchange reaches 80% on the zeolite, while the zeolite structure is preserved during the process. La3+-FAU-type X-zeolites showed the same extreme affinity towards 1,2,3,4 TeCDD as Na+ - FAU-type X-zeolites did for 2,3-DCDD. At the same time it could be shown that both dioxins could be separated by adsorption, while 1,2,3,4 TeCDD only interacts with the external surface of Na+-FAU-type X-zeolite, not entering the zeolite pores. (C) 2015 Elsevier Inc. All rights reserved

Microporous Stilbite single crystals for alcohol sensing

International audienc

Adsorption properties of zeolites for artificial kidney applications

International audienc