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Lithium cobaltate (LiCoO2) and lithium manganate (LiMn2O4) were synthesized by self-propagating high-temperature combustion and their phase purity and composition were characterized by X-ray diffraction and inductively coupled plasma spectroscopy. These transition metal oxides were mechanically immobilized on the surface of paraffin-impregnated graphite electrodes and their cyclic voltammetric behaviour in aqueous alkali electrolytes was examined. It was shown that both the oxides undergo proton insertion upon the reduction of Co3+ to Co2+ in LiCoO2 and Mn4+ to Mn3+ in LiMn2O4, while they deintercalate protons on the reverse oxidation. Scanning electron microscopy reveals spherical LiCoO2 particles with a very narrow size distribution. Energy dispersive X-ray detection proved the absence of metal cation intercalation. [ABSTRACT FROM AUTHOR]

Sensors with solid electrolytes provide the possibility of correct and fast measurements of partial pressures of various gases. By modification of the solid electrolyte, sensors with specific performances may be manufactured. Layers of Na+-, Li+-, Ca2+- and Sr2+-β“-alumina on top of polycrystalline α-alumina substrates were produced by an in-situ formation process and were used as solid electrolytes for CO2 and SOx sensors. Carbonates and sulphates were applied as measuring electrodes and oxidic mixtures of SiO2 and silicates were used as reference electrodes. The different performance of these sensors was investigated over a wide temperature range and the results were compared with theoretical data. Different solid electrolyte / electrode combinations were applied, which all showed different characteristic cross sensitivities against water and organic components. [ABSTRACT FROM AUTHOR]