A new generation of nanostructured cathodes for intermediate temperature solid-oxide fuel cells, with very low polarization resistance, is presented. They were prepared from cobaltite nanotubes using a fast and simple method that allows the retention of the original nanostructure.

We present a phenomenological model based on the thermodynamics of the phase separated state of manganites, accounting for its static and dynamic properties. Through calorimetric measurements on La0.225Pr0.40Ca0.375MnO3 the low temperature free energies of the coexisting ferromagnetic and charge ordered phases are evaluated. The phase separated state is modeled by free energy densities uniformly spread over the sample volume. The calculations contemplate the out of equilibrium features of the coexisting phase regime, to allow a comparison between magnetic measurements and the predictions of the model. A phase diagram including the static and dynamic properties of the system is constructed, showing the existence of blocked and unblocked regimes which are characteristics of the phase separated state in manganites.

In this work, ZrO2−CeO2 mixed oxide nanotubes with 50, 70, and 90 mol % CeO2 were synthesized following a very simple, high yield procedure, and their properties were characterized by synchrotron radiation XRD and by high resolution electron microscopy. The 50, 70, and 90 mol % CeO2 nanotubes exhibited the tetragonal phase (t′-form and t′′-form, P42/nmc space group) or the cubic phase (Fm3m space group). The nanotube walls were composed of nanoparticles with an average crystallite size ranging from 4.7 to 7.6 nm. Electron microscopy observations confirmed the size of these nanoparticles by direct observation. The SEM and TEM results showed that individual nanotubes were composed of a curved sheet of these nanoparticles. By SEM analysis, the nanotubes were found to have lengths of around 1−8 μm, diameters of around 500 nm, and wall thicknesses of 20 nm. Elemental analysis showed that Ce:Zr ratios appeared to be constant across space, suggesting compositional homogeneity in the samples. The 90 mol % CeO2 nanotubes exhibited the highest value of specific surface area, 101 m2·g−1, which compared with about 28 m2·g−1 for the other two compositions.