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Metal exsolution reactions enable the preparation of metal-oxide nano-composites from oxide parent materials in a single thermal reduction step. In this process, reducible metals are released from the doped oxide and nucleate in the form of finely dispersed, supported nanoparticles. A reversible exsolution and re-dissolution reaction could provide an effective way to regenerate catalysts, where the surface structure and functionality dynamically adapt to the ambient gas environment. However, the reversibility of exsolution reactions is often limited. We investigate reversibility limitations in the niobium and nickel co-doped perovskite SrTi0.95−xNb0.05NixO3−δ with varying Ni doping concentrations between x = 0.005-0.1. Combined morphological, structural and chemical analyses of the material response upon consecutive thermal treatments in reducing and oxidizing environments reveal a non-correlated bulk and surface response of the material upon redox treatment. While the bulk structural changes are mostly reversible, no re-dissolution of the exsolved surface nanoparticles is detected for the investigated time-temperature window (T = 800 °C, t = 5 h for reduction and reoxidation, respectively). Instead, a modification in the nanoparticle distribution and an increased surface wetting of the support by the exsolved metal species are observed upon reoxidation of the nanoparticles.

Lithium and sodium (Na) mixed polyanion solid electrolytes for all-solid-state batteries display some of the highest ionic conductivities reported to date. However, the effect of polyanion mixing on the ion-transport properties is still not fully understood. Here, we focus on Na1+xZr2SixP3-xO12 (0 ≤ x ≤ 3) NASICON electrolyte to elucidate the role of polyanion mixing on the Na-ion transport properties. Although NASICON is a widely investigated system, transport properties derived from experiments or theory vary by orders of magnitude. We use more than 2000 distinct ab initio-based kinetic Monte Carlo simulations to map the compositional space of NASICON over various time ranges, spatial resolutions and temperatures. Via electrochemical impedance spectroscopy measurements on samples with different sodium content, we find that the highest ionic conductivity (i.e., about 0.165 S cm-1 at 473 K) is experimentally achieved in Na3.4Zr2Si2.4P0.6O12, in line with simulations (i.e., about 0.170 S cm-1 at 473 K). The theoretical studies indicate that doped NASICON compounds (especially those with a silicon content x ≥ 2.4) can improve the Na-ion mobility compared to undoped NASICON compositions.

Acceptor-substituted Ba(Zr,Ce)O3 proton conducting oxides have attracted significant attention due to their excellent proton conductivity at intermediate temperatures (400–600 °C). A high Zr/Ce ratio is crucial for maintaining stability in humid or other harsh atmospheres. Herein, a systematic study was conducted on the phase composition, microstructure, and the resulting hydration ability and electrochemical performance of high Zr/Ce ratio Ba(Zr,Ce)O3 solid solutions with different Y substitution levels (10 at% to 30 at%). In this substitution range, no apparent secondary phase can be found from XRD, leading to a continuous increase in hydration content. A Y-rich phase was observed in SEM for compositions with high levels of Y substitution. The impact of Y on proton conduction was examined using EIS, with particular attention on elucidating the effects of varying amounts of Y on bulk proton conduction. The increase of proton conductivity was primarily due to the increased charge carrier (proton) concentration caused by Y substitution. Different concentrations of Y have little effect on proton mobility, indicating a compromise between different mechanisms such as the Y trapping effect and the nano-percolation effect. Grain boundary proton conduction was discussed combining the TEM-EDS results to explain the space charge layer effect. Mechanical properties and thermo-chemical stability were also considered to pave the way for real applications. [ABSTRACT FROM AUTHOR]

Li-rich layered oxides can potentially provide high capacity, thereby enhancing energy density as cathode materials in Li-ion batteries. However, one of the main drawbacks is their low cycling stability. It has been proposed that the structural stability of a solid solution compound might be enhanced by exploiting the high-entropy concept. Here, we studied two Li-rich layered oxide cathode materials with multiple cations in their transition metal sites, categorized as medium or high entropy: Li(Li0.2Co0.18Ni0.18Mn0.44)O2 and Li(Li0.2Co0.18Ni0.18Mn0.18Ti0.26)O2. The synthesized materials, however, experienced a large capacity loss during the first charge/discharge cycle. We performed first-principles calculations to understand the mechanism behind the capacity fading and discovered significant structural changes in both systems. Specifically, we observed extensive Li/Ni interchange, migration of transition metal ions to Li sites, and formation of secondary phases. For the Ti-containing material, which shows a larger capacity fade than the other system, we even observed the formation of a spinel phase. The computed enthalpies of secondary phase formation reactions exhibit large negative values. However, the estimated (maximum) configurational entropy contributions to the free energies of these reactions are much smaller and therefore not determining factors. This study provides crucial insights into degradation mechanisms in Li-rich high-entropy systems, aiding the future design and development of advanced cathode materials for next-generation lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Gadolinium zirconate (Gd2Zr2O7, GZO) has been investigated for two decades as a thermal barrier coating (TBC) material in gas turbines. The advantages of this material over conventional yttria-stabilized zirconia (YSZ) are its lower thermal conductivity, phase stability, and low sintering tendency at elevated temperatures above 1200 °C. However, a major disadvantage is the low fracture toughness of the material and the reaction with the thermally growing oxide layer (TGO). As a result, single-layer GZO coatings cannot be used as TBCs. To overcome these challenges, the present study focuses on the development of double-layer TBC systems, produced with a single gun to keep the manufacturing time low. The respective layers were optimized for specific requirements using a porous atmospheric plasma spray (APS)-YSZ interlayer covered by a suspension plasma sprayed (SPS)-GZO top layer. In furnace cycling tests at 1100 °C, the double-layer systems developed in this study were able to achieve a significant increase in thermal cycle life compared to single-layer APS-YSZ coatings. In addition, the failure mechanism after thermal cycling was investigated, and phase analysis was performed using XRD. The examination of Young's modulus and the hardness of the layers revealed sintering in the GZO layer due to thermal cycling, while the APS layer showed only minor changes. [ABSTRACT FROM AUTHOR]

Solid–state batteries based on Li7La3Zr2O12 (LLZO) garnet electrolyte are a robust and safe alternative to conventional lithium‐ion batteries. However, the large‐scale implementation of ceramic composite cathodes is still challenging due to a complex multistep manufacturing process. A new one‐step route for the direct synthesis of LLZO during the manufacturing of LLZO/LiCoO2 (LCO) composite cathodes based on cheap precursors and utilizing the industrially established tape casting process is presented. It is shown that Al, Ta:LLZO can be formed directly in the presence of LCO from metal oxide precursors (LiOH, La2O3, ZrO2, Al2O3, and Ta2O5) by heating to 1050 °C, eliminating the time‐ and energy‐consuming synthesis of preformed LLZO powders. In addition, performance‐optimized gradient microstructures can be produced by sequential casting of slurries with different compositions, resulting in dense and flat phase‐pure cathodes without unwanted ion interdiffusion or secondary phase formation. Freestanding cathodes with a thickness of 85 µm, a relative density of 95%, and an industrial relevant LCO loading of 15 mg show an initial capacity of 82 mAh g−1 (63% of the theoretical capacity of LCO) in a solid‐state cell with Li metal anodes, which is comparable to conventional LCO/LLZO cathodes and can be further improved in the future. [ABSTRACT FROM AUTHOR]

Plasma etching is a crucial step in semiconductor manufacturing. High cleanliness and wafer‐to‐wafer reproducibility in the etching chamber are essential in order to successfully achieve nanometer‐sized integrated functions on the wafer. The trend toward the application of more aggressive plasma compositions leads to higher demands on the plasma resistance of the materials used in the etching chamber. Due to its excellent etch resistance, yttrium aluminum garnet Y3Al5O12 (YAG) is starting to replace established materials like SiO2 or Al2O3 in this kind of application. In this study, reactive spark plasma sintering (SPS) was used to manufacture highly dense YAG ceramics from the respective oxides. In addition, yttrium was replaced with heavier lanthanoids (Er, Lu), intending to investigate the role of the A‐site cation in the garnet type structure on the plasma erosion behavior. The produced materials were exposed to fluorine‐based etching plasmas mimicking the conditions in the semiconductor manufacturing apparatus and the erosion behavior was characterized by atomic force microscopy (AFM), secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), and profilometry. The induced chemical gradient in the samples is limited to a few nanometers below the surface, which makes its characterization challenging. For advanced analysis, we developed a correlative characterization method combining SIMS and scanning TEM (STEM)–energy‐dispersive spectroscopy (EDS) enabling us to examine the structural and chemical changes in the reaction layer locally resolved. In the case of lanthanoid aluminates, an altered reaction layer and reduced fluorine penetration compared to YAG were found. However, a correlation between the characteristics of the induced chemical gradient and the determined physical erosion rates was not evident. [ABSTRACT FROM AUTHOR]