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New emerging disciplines are specifically devoted to study trivial and non-trivial effects resulting from working in the nanoscale, however, the implementation of these nanostructures in real devices is still a major challenge. Thin film deposition and silicon microtechnology is probably the most promising and straightforward combination for the reliable integration of nanomaterials in real devices. In particular, the implementation of pure ionic and mixed ionic/electronic conductors (MIECs) in thin film form allows the miniaturization of multiple solid state devices such as solid oxide fuel cells (SOFCs). In this work, we will present the implementation of novel nanoionics concepts in micro-SOFCs by using micro and nanofabrication technologies. We will put special attention on the contribution of grain boundaries to the mass transport properties in interface-dominated materials such as thin films. Grain boundary engineering will be presented as a powerful tool for reducing the resistance associated to electrolytes and even control the intrinsic transport nature and performance of MIEC materials.

Molecular Dynamics simulations of ordered and disordered versions of a gadolinium barium cobaltite have been performed for the temperature range between 800K and 1400K. Oxygen diffusivity for the ordered and disordered phase was compared resulting in an analysis of the effect of cationic ordering on the oxygen mass transport properties.

Mesoporous nickel-ceria cermets were synthesized and electrically characterized as anodes for intermediate-temperature solid oxide fuel cells using Ce0.8Gd0.2O1.9 as the material for the electrolyte. Mesoporous nickel-ceria cermets were prepared from silica hard templates, with KIT-6 structure, and a multistep impregnation process. A comprehensive (micro)structural analysis was carried out in order to determine the stability of the replicated mesoporous cermet at the typical processing temperatures employed in solid oxide fuel cells fabrication, i.e. from 900oC to 1100oC. Electrical characterization of the mesoporous cermets in symmetrical cells was carried out in humidified 5%H2 in N2 atmosphere. Targeted values of electrode/electrolyte area specific resistance were achieved in the intermediate temperature range showing the suitability of the here-presented mesoporous approach for developing a new class of high performance anodes for IT-SOFC.

The present study is devoted to analyze the compatibility of yttria-stabilized zirconia thin films prepared by pulsed laser deposition technique for developing new silicon-based micro devices for micro solid oxide fuel cells applications. Yttria-stabilized zirconia free-standing membranes with thicknesses from 60 to 240 nm and surface areas between 50x50 µm2 and 820x820 µm2 were fabricated on micromachined Si/SiO2/Si3N4 substrates. Deposition process was optimized for deposition temperatures from 200ºC to 800ºC. A mechanical study comprising thermomechanical stability, residual stress of the membranes and annealing treatment as well as a preliminary electrical characterization of ionic conductivity was performed in order to evaluate the best processing parameters for the yttria-stabilized zirconia membranes.