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Ba0.5Sr0.5Co0.8Fe0.2O3-δ thin films were grown by pulsed laser deposition (PLD) in the temperature range from room temperature (RT) to 1073 K and at oxygen pressures from 6.66 to 39.99 Pa in order to produce dense defect-free thin films. Si with a native oxide layer and MgO were used as the substrate materials. The structure of the thin films was highly dependent on substrate temperature, material and oxygen partial pressure, leading to formation of different microstructures - pores, cracks, columnar and fibrous grains. Cracks and delamination of the thin films were observed in dense layers at higher temperatures, while this was not the case with the columnar thin films. Differences in thermal expansion coefficient, phase transformation and oxygen non-stoichiometry of BSCF are possible explanations for the cracking of the dense thin films. Thin films with a columnar structure are positively influenced by annealing inducing grain growth and densification. [ABSTRACT FROM AUTHOR]

Next-generation micro-solid oxide fuel cells for portable devices require nanocrystalline thin-film electrolytes in order to allow fuel cell fabrication on chips at a low operation temperature and with high power outputs. In this study, nanocrystalline gadolinia-doped ceria (Ce0.8Gd0.2O1.9− x) thin-film electrolytes are fabricated and their electrical conductivity and thermodynamic stability are evaluated with respect to microstructure. Nanocrystalline gadolinia-doped ceria thin-film material (Ce0.8Gd0.2O1.9− x) exhibits a larger amount of defects due to strain in the film than state-of-the-art microcrystalline bulk material. This strain in the film decreases the ionic conductivity of this ionic O2− conductor. The thermodynamic stability of a nanocrystalline ceria solid solution with 65 nm grain size is reduced compared with microcrystalline material with 3–5 μm grain size. Nanocrystalline spray-pyrolyzed and PLD Ce0.8Gd0.2O1.9− x thin films with average grain sizes larger than 70 nm show predominantly ionic conductivity for temperatures lower than 700°C, which is high enough to be potentially used as electrolytes in low to intermediate-temperature micro-solid oxide fuel cells. [ABSTRACT FROM AUTHOR]