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The synthesis of yttria‐stabilized zirconia nanoparticles with a fine control on the chemical composition and the distribution of yttrium cations is of major interest to master the mechanical, optical or ionic conduction properties of the final material. However, a fine control of this chemical homogeneity within the particles, especially above 5 mol.% of yttria (Y2O3), is challenging with conventional synthesis routes. In the present study, for the first time the interest of using supercritical sol–gel like synthesis is demonstrated for the continuous production in a single step of high quality zirconia (ZrO2) nanocrystals of 7 nm stabilized with Y2O3 without post‐treatment. Three compositions are investigated, i.e., 1.5, 3, and 8 mol.% of Y2O3 and in‐depth physico‐ chemical characterizations such as X‐ray diffraction, total X‐ray scattering, High‐resolution electron microscopy, Raman and X‐ray photoelectron spectroscopy are performed to asses and thus prove the successful synthesis of these different compositions while keeping a good chemical homogeneity. This enables to confirm that this original process leads to a unique and fine structural control for such small yttria‐doped zirconia nanocrystals. [ABSTRACT FROM AUTHOR]

The production of BaTi1-yZryO3 (0 ≤ y ≤ 1, BTZ) nanocrystals is known to be challenging due the low reactivity of zirconium precursors. Here we have successfully studied the impact of zirconium on the BTZ particle formation in sub- and supercritical fluid conditions along the entire solid solution. In situ synchrotron wide angle X-ray scattering (WAXS) analyses were conducted in batch at 150 and 400 °C to follow, in real time, the BTZ crystallite synthesis. This approach revealed the complexity behind the nucleation and growth mechanisms of ABO3 nanocrystals, especially toward high zirconium content (more than 50 atomic %). This type of substitution induces, among other things, microstrain within the structure. Moreover, for the cases of BaTi0.4Zr0.6O3 and BaTi0.2Zr0.8O3, the experiments showed the apparition of two crystallite size populations. In the BaTi0.4Zr0.6O3 case, at 400 °C, these two size populations merged into a single one after at least 8 min; in contrast to what was observed for the case of BaTi0.2Zr0.8O3. This is a manifestation of how with increasing the zirconium content the particles become more refractory and in these cases the temperature is not high enough to enable their ripening. It is important to note that this behavior was not observed for particles produced at 400 °C using a flow synthesis method, with a residence time of only 50 s. There, the particles presented a single size population close to the one obtained after 8 min in batch. This thus suggests that for batch syntheses a longer time is required to achieve a similar product quality to the one obtained with a flow process. [ABSTRACT FROM AUTHOR]

Metal‐insulator‐metal (MIM) capacitors with Ba0.6Sr0.4TiO3 (BST) thin films as insulating layers are fabricated using a novel, fast, and low‐cost method. On one hand, the process lies in the swift, continuous, and scalable synthesis of BST nanoparticles using the supercritical fluid technology and, on the other hand, the nonpyrolytic spray coating of thin films using colloidal nanocrystals as ink. The authors focus on the deposition process of thin and uniform layer. A dispersed colloidal suspension based on BST nanoparticles is deposited on a hot copper substrate. A 200 nm thick dielectric film is successfully obtained. Electrical characterizations of Cu/BST/Al MIM structure demonstrate a state‐of‐the‐art capacitance density almost reaching 1 µF cm−2 within an operating voltage range of ±1 V. Moreover, an annealing process of the dielectric layer and the final MIM capacitor at 90 °C during 15 h brings a significant decrease of the leakage current by three decades from mA cm−2 to µA cm−2. Spray coating of colloidal suspensions based on Ba0.6Sr0.4TiO3(BST) nanoparticles enables the deposition of uniform thin films (200 ± 50 nm). Electrical characterizations of these films demonstrate state‐of‐the‐art capacitance density (0.9 µF cm−2). The annealing of the BST film and the final metal‐insulator‐metal (MIM) capacitor reduce the leakage current by three decades (from mA cm−2 down to µA cm2). [ABSTRACT FROM AUTHOR]

The thermodynamic stability of nanocrystals is different from that of bulk systems, and nanoscale phase diagrams are to a large degree unknown. Here we present a systematic investigation of the Pt1-xRux phase diagram through supercritical flow synthesis of Pt1-xRux nanoparticles across the entire compositional range. The synthesis was done in stoichiometric steps of 0.1 using an ethanol-toluene mixture as solvent at 450 °C and 200 bar. The products were characterized by high-resolution synchrotron powder X-ray diffraction, transmission electron microscopy, and elemental mapping of individual particles using energy-dispersive X-ray spectroscopy. The diffraction data revealed a single-phase face-centered cubic (fcc) alloy for x ≤ 0.2, while an additional hexagonal close-packed (hcp) phase emerges as x approaches 1. This behavior deviates significantly from the bulk phase diagram, where a biphasic region is only observed for 0.62 < x < 0.8. Thus, compositional design of Pt-Ru alloys is more flexible on the nanoscale, opening up significant possibilities for catalyst optimization. Rietveld refinements and microstructural line profile analysis show that the fcc unit cell dimensions follow Vegard's law within a good approximation. On the other hand, crystallite size, microstrain, phase content, and hcp c/a ratio depend nonlinearly on x but show some correlation to the bulk phase diagram. Elemental mapping shows the nanoparticles to be homogeneous, but in some cases, fcc-hcp phase boundaries and modulations in the elemental distribution were observed. All samples below x < 0.3 exhibit a spherical morphology. At higher ruthenium content, x ≥ 0.3, another morphology emerges with elongated particles together with the dominating spherical mophology. The TEM average particle sizes range from 5.0(8) to 10.4(7) nm. [ABSTRACT FROM AUTHOR]