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Self-generated composites from the series BaCe1-(x+z)FexYzO3-ẟ with z=0.2 for 0.1≤x≤0.6 and z=0 for Ce:Fe = 1 were obtained by one-pot synthesis. The composites consist of proton and electron conducting phases and are interesting as electrode materials for protonic ceramic fuel and electrolyser cells. X-ray diffraction with quantitative phase analysis and scanning electron microscopy with energy-dispersive X-ray spectroscopy showed that the materials consist of Fe-rich phases and a Ce-rich perovskite phase, which are present in the corresponding proportion depending on the precursor composition (Ce-Fe ratio). Substitution with Y leads to a narrowing of the miscibility gap compared to BaCe1-xFexO3-ẟ composites, thus favouring transformation of the composites into single cubic phases at temperatures above 1000°C. Further, Y influences the mutual solubility of Fe3+/4+ and Ce4+ in the Ce-rich and Fe-rich phase, respectively, as shown elemental mapping via scanning transmission electron microscopy. As only a small proportion of the Y dissolves in the electrolyte-type phase, the increased proton uptake resulting from the incorporation of Y in the Ce-rich phase is limited. Strategies to overcome this limitation by substitution with ions with similar ionic radii, but different basicity, are discussed.

Compounds from the series La0.8-xNdxCa0.2FeO3-δ (0.1 ≤ x ≤ 0.7) were synthesised by a sol–gel route. X-ray diffraction and Rietveld analysis showed that materials with 0 ≤ x ≤ 0.6 crystallize as single-phase orthorhombic perovskites. The smaller ionic radius of Nd3+ compared to La3+ leads to a decrease in unit cell volume with increasing x. Elemental mapping by high-resolution scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy confirms the homogeneous distribution of the A-site elements (La, Nd and Ca) in the perovskite (ABO3) lattice. The thermal expansion behaviour of La0.8-xNdxCa0.2FeO3-δ (0 ≤ x ≤ 0.6) was characterized by dilatometry at 30 ≤ T/°C ≤ 1000 and 1 × 10–3 ≤ pO2/bar ≤ 1. The thermal expansion coefficients of La0.8-xNdxCa0.2FeO3-δ, which were determined in regions I (40–530 °C) and II (530–990 °C), respectively, are almost independent of the Nd concentration in the range of (0 ≤ x ≤ 0.6) and increase slightly with decreasing pO2. The transition from orthorhombic to trigonal modification, which is observed for La0.8Ca0.2FeO3-δ at approx. 740 °C, is suppressed for all Nd-substituted compounds with x ≥ 0.1.

Micro- and nanostructure investigations of AlSi10Mg alloy powders and additive manufactured samples were performed to highlight common effects related to very fast local cooling rates during production. We refer to the homogenously dispersed Si(Mg) nanoparticles and the presence of interconnected amorphous phases in the coral-like eutectic Si network and their evolution upon in-situ heating in scanning transmission electron microscope. The in-situ heating experiments showed as first phenomenon at lower temperatures the crystallization of the eventually present amorphous silicon, while at temperatures above 240 °C coarsening into spherical crystalline particles and network breakage prevail. In addition, the Si nanoparticles evolved, mainly changing their shape and coherence with the matrix. These findings correlate with results from macroscopic investigations (DSC, in-situ XRD), where they further contribute to explain the retrieved exothermic signals by linking them to the respective crystallization of the amorphous Si network, the coarsening of the finely dispersed Si nanocrystals and network breakage.

Long-term stability tests are performed at 800 °C on Pr2NiO4+δ air electrodes by use of a symmetrical button cell with Ce0.9Gd0.1O1.95 as solid electrolyte. The experiments are carried out by means of electrochemical impedance spectroscopy and current-voltage measurements with and without current load under dry and humid conditions in the presence of a chromium source. Chromium poisoning of Pr2NiO4+δ air electrodes is investigated for periods of several hundred hours at 30% relative humidity. In order to separate the influence of anodic and cathodic electrode polarization on Cr-deposition, measurements are conducted using a Pt-reference electrode. The electrode performance is found to remain fairly stable under dry conditions, even when a current is drawn. However, after volatile Cr-species in a humid atmosphere are introduced, the cell performance starts to deteriorate and the polarization resistance contribution of the SOFC cathode increases significantly. After several thousand hours, the electrodes are analyzed by means of analytical electron microscopy. Detailed post-test analyses provide evidence for a correlation between the extent of Cr-deposition and electrode degradation in SOFC as well as SOEC mode. Based on these findings, enhanced resilience of Pr2NiO4+δ against Cr-poisoning in SOEC mode can be established.