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Electrochemical reaction-based, proton-conducting, solid oxide fuel cells (PC-SOFCs), which operate at a medium temperature range from 300 to 600 °C, are expected to become a new source of renewable energy. Using electron–ion mixed conductor material for PC-SOFC anode and cathode electrode membranes can enhance the performance of their electrochemical reactions. To realize such novel anode electrode materials for PC-SOFCs, BaCe0.4Pr0.4Y0.2O3−δ (BCPY) thin films were prepared on an Al2O3 (0001) substrate by RF magnetron sputtering. The amount of oxygen vacancies in the BCPY thin films was quantitatively evaluated by X-ray absorption spectroscopy and defect chemical analysis in order to investigate hole-proton mixed conductivity. Proton conductivity was suggested from the O 1s photoemission spectrum showing an O–H bond peak formed on the oxygen ion sites. Hole conductivity was suggested from the energy difference between the top of the valence band and the Fermi level being close to the activation energy, which was estimated from Arrhenius plots. The subject wet-annealed BCPY thinner films, which exhibit surface hole-proton mixed conductivity of more than 10−2 S·K/cm at 300 °C, can be applied as a new anode electrode material for PC-SOFC operating in the medium temperature range. [ABSTRACT FROM AUTHOR]

Amorphous ZrO2 and YSZ thin films with controlled microstructures were fabricated using PLD with an ArF excimer laser at room temperature, so as to attain high proton conductivity without the use of high temperature annealing. The density of the film was largely modulated from 5.9 to 1.6 g cm−3 by varying the PO2 condition during deposition. In the resulting relatively porous thin films, proton conductivity increased rapidly near room temperature with an activation energy as large as −2.5 eV, reaching 6.66 × 10−4 S cm−1 for ZrO2 and 1.38 × 10−4 S cm−1 for YSZ thin films. The proton conductivity obtained in this study was higher than that exhibited by polycrystalline YSZ pellets (∼10−5 S cm−1), even though the employed thin films were amorphous. To date, such high proton conductivity has been achieved only with polycrystalline YSZ thin films, which require the use of a high temperature annealing process. These results indicate that the origin of the high proton conductivity is attributed to variations in porosity and the local structure around Zr atoms which are controlled by the PO2 levels. The present study evidences that a solid electrolyte thin film with high proton conductivity can be fabricated at room temperature throughout the fabrication process, which in turn expands the applicability of proton-conducting solid electrolytes to a wide range of electrochemical devices. [ABSTRACT FROM AUTHOR]

We investigated the nanoionics-based neuromorphic function of Pt/Ti0.96Co0.04O2− δ /Pt multilayers with a cross-point structure prepared by RF magnetron sputtering. This multilayer exhibits electro-ion mixed conduction and a nonlinear current–voltage characteristic based on the Schottky barrier between Pt and Ti0.96Co0.04O2− δ layers. When the low electrical pulse of 0.8 V was applied with a short interval time of 14 s, current modulation corresponding to the long-term memorization (LTM) was observed, though the current response at the long interval time of 80 s was the short-term memorization (STM). The O 1 s photoemission spectrum showed the OH− peak that contributes to the electron-ion mixed conduction. The current responses with both LTM and STM are considered to be due to the local proton migration at near the Schottky barrier. [ABSTRACT FROM AUTHOR]

Ce0.80Sm0.20O2− δ thin films with (111) orientation were prepared on (0001) Al2O3 substrates by RF magnetron sputtering. The Ce3+ valence ratios, which are closely related to the oxygen vacancies' concentration, of the as-deposited and wet-annealed thin films were 37.8% and 29.3%, respectively. These thin films exhibited oxygen ion related conduction in the medium-temperature region of 800 to 200 °C. Below 100 °C, the conductivity (σ) of the wet-annealed thin film increased as the temperature (T) decreased and the σT value was ∼1.0 S cm−1 K at 25 °C. The O 1 s photoemission spectrum exhibited H2O and OH− peaks on the surface. The above results indicate that the protons on the surface of the wet-annealed thin film actively migrated through the physisorbed water layer by the Grotthuss mechanism. [ABSTRACT FROM AUTHOR]

The electric double layer (EDL) effect at solid electrolyte/electrode interfaces has been a key topic in many energy and nanoelectronics applications (e.g., all-solid-state Li+ batteries and memristors). However, its characterization remains difficult in comparison with liquid electrolytes. Herein, we use a novel method to show that the EDL effect, and its suppression at solid electrolyte/electronic material interfaces, can be characterized on the basis of the electric conduction characteristics of hydrogenated diamond(H-diamond)-based EDL transistors (EDLTs). Whereas H-diamond-based EDLT with a Li-Si-Zr-O Li+ solid electrolyte showed EDL-induced hole density modulation over a range of up to three orders of magnitude, EDLT with a Li-La-Ti-O (LLTO) Li+ solid electrolyte showed negligible enhancement, which indicates strong suppression of the EDL effect. Such suppression is attributed to charge neutralization in the LLTO, which is due to variation in the valence state of the Ti ions present. The method described is useful for quantitatively evaluating the EDL effect in various solid electrolytes. The effect of the electric double layer with solid electrolytes remains hard to characterize. In this study, the authors show how to evaluate the electric double layer effect with various lithium solid electrolytes using a hydrogenated diamond-based transistor. [ABSTRACT FROM AUTHOR]

Scandium (Sc) and yttrium (Y) co-doped ZrO2 (ScYSZ) thin films were prepared on a SiO2-Si substrate via pulsed laser deposition (PLD) method. In order to obtain good quality thin films with the desired microstructure, various oxygen partial pressures ( P O 2 ) from 0.01 Pa to 10 Pa and substrate temperatures (Ts) from 25 °C to 800 °C were investigated. X-ray diffraction (XRD) patterns results showed that amorphous ScYSZ thin films were formed at room substrate temperature while cubic polycrystalline thin films were obtained at higher substrate temperatures (Ts = 200 °C, 400 °C, 600 °C, 800 °C). Raman spectra revealed a distinct Raman shift at around 600 cm−1 supporting a cubic phase. However, a transition from cubic to tetragonal phase can be observed with increasing oxygen partial pressure. Photoemission spectroscopy (PES) spectra suggested supporting analysis that more oxygen vacancies in the lattice can be observed for samples deposited at lower oxygen partial pressures resulting in a cubic structure with higher dopant cation binding energies as compared to the tetragonal structure observed at higher oxygen partial pressure. On the other hand, dense morphologies can be obtained at lower   P O 2 (0.01 Pa and 0.1 Pa) while more porous morphologies can be obtained at higher P O 2 (1.0 Pa and 10 Pa). [ABSTRACT FROM AUTHOR]