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Although cold sintering remains an emerging processing technique, it is noteworthy to consider recent progress in materials that are of interest to electrochemical systems with elevated service temperatures. Here we discuss a broad number of materials ranging from alkali electrolytes for solid state batteries, to oxygen ion conductors for gas sensing. We also discuss the opportunity to co-fire mixed ionic conductors into multilayered devices. Given the low-temperature sintering temperatures with the cold sintering process (CSP), we will discuss some insights into operating ceramics at temperatures near or above their processing temperature.

Electrochemical Impedance Spectroscopy (EIS) is a very powerful method for analyzing electrochemical systems with respect to the factors impacting conductivity, charge transfer and diffusion. A great advantage of EIS is that the system under test (SUT) can be measured in operando so that the SUT can be characterized under conditions as they prevail in a fully functional technical system – as compared to model cells where only certain properties are tested under well-defined conditions. The small-signal excitation ensures that the SUT remains in its predefined operating point. Those aspects are of great importance when trying to optimize devices for commercial application. However, some characteristics can only be assessed through dynamic measurements with macroscopic external triggers. For example, grain boundary potential barriers in oxygen ion conductors can be well characterized in steady-state by EIS. With an external bias voltage, the resistance of the grain boundaries can be decreased, and the magnitude of this decrease can also be determined very accurately by EIS. However, while the resistance shrinks, further information about how the bias impacts the grain boundaries remains elusive. Is it a direct voltage effect or does the charge carrier and dopant concentration change within and adjacent to the grain boundary? The dynamic evolution of relevant parameters during the transition when changing the bias voltage can help to provide the additional information required for a more incisive analysis. Classic EIS is not applicable for such measurements because the steady-state condition is one of the fundamental requirements for EIS. In the field of semiconductors, deep-level transient spectroscopy (DLTS) is an established technique to determine the energy levels of certain defects. Hereby, the capacity at high frequencies is monitored continuously during voltage or light pulses at different temperatures. The temperature at which the pulses impact the capacity is an indicator for the thermal energy required to activate those defects. With this information, their energy level within the band structure can be calculated. This is comparable to the concept of single-frequency EIS (SFEIS), where the impedance at one specific frequency is measured continuously. For example, high-frequency SFEIS measurements have been used to determine the temperature evolution in a fuel cell or battery by relating the Ohmic resistance to the electrolyte temperature. It might not be possible to measure full spectra during an externally triggered system transition, but it is possible to dynamically monitor the impedance at a specific frequency and analyze its dynamics in the time domain. Resistance or capacitance can both be used as indicative parameters for a specific process or behavior. In this study, we analyze the grain boundary resistance of a 3% Gd-doped CeO2 (GDC) thin film. GDC is one of the most prominent oxygen ion conductors but suffers, at lower doping levels, from a large grain boundary resistance that makes polycrystalline samples two to three orders of magnitude more resistive than single crystals. The additional resistance is caused, in large part, by the space-charge zone and associated potential barrier due to the positive charge of the grain boundary core. It is known that the grain boundary resistance of GDC decreases upon biasing with an external voltage. Recently, our group has demonstrated that illuminating the sample with light above the band-gap has a similar effect on the resistance. Basically, the light creates electrons and holes, that are able to compensate the space-charge and flatten the bands as generally assumed for photoelectrochemical systems. We measure the dynamic evolution of resistance and capacitance of a GDC thin film upon bias with voltage and light pulses. Then, we analyze the obtained time domain evolutions, to clarify the exact mechanisms that leads to the resistance decrease in each case. The method presented here nicely compliments a classic EIS analysis, where spectra recorded in two different static operating points represent the characteristics of the system in both states in equilibrium. The evolution of relevant parameters, such as capacitance and resistance at a certain frequency, can provide additional information about the causes and dynamics of the changes and thereby provide more information on the exact mechanism and the driving force. This work was supported by JSPS Core-to-Core Program, A. Advanced Research Networks: “Solid Oxide Interfaces for Faster Ion Transport”, Department of Energy, Basic Energy Sciences and the Swiss National Science Foundation. Figure 1

During the magnetron plasma sputtering process, the bombardment effects of the negative oxygen ions (NOIs) on the thin film properties of amorphous indium-gallium-zinc oxide (a-IGZO) has been investigated. While the kinetic energies of NOIs effectively adjusting by using a superimposed rf/dc magnetron sputtering system, the characteristics of NOIs extracted by in situ analyses with ion energy analyzer are good agreement with the calculated values by the Kevin Meyer equation as shown in Figs 1(a) and 1(b). Furthermore, we find that the observed energies of NOIs corresponding to the applied dc bias are enough high to influence a lattice distortion and/or displacement in a-IGZO thin films. Figure 2(a) and 2(b) show the results of the Hall measurement and work function of a-IGZO films at RT with different dc biases. The σ and ne of a-IGZO films monotonically increases with increasing the dc bias in logarithmic scale. This is due to the increment in the ne as a function of dc bias. Interestingly, the hall mobility (μhall ) drops rapidly with opposite direction against that of ne , and σ until under the dc bias of 300V, and becomes flat over 300V. In general, μhall largely depends on ne in AOSs & TCOs owing to their structural randomness; μhall of AOS thin film increases with ne , while that of TCO decreases with ne . However, the observed ne (> 1019 cm-3) of IGZO films with relatively higher dc bias is too high as well as that of TCOs. It is obvious that the variation of σ, ne , and μhall above the dc bias of 300 V is quite different with that of the measured values at relatively lower dc bias (< 300 V). Furthermore, Fig. 2(b) shows the workfunction of a-IGZO films extracted by a kelvin probe method monotonically decreases from 4.986 to 4.940 eV with increasing the dc bias from 100 to 400 V, but it has also a knee point around the dc bias of 300 V. The overall analysis revealed that the bombardment of NOIs with high energy has a great influence on a-IGZO film properties. Our work demonstrates the bombardment of NOIs is one of a crucial issue to achieve the high quality a-IGZO films.

To investigate the oxygen ion diffusion behavior in an SOFC typically constructed of an LSCF cathode, a GDC interlayer and a YSZ electrolyte, where an SrZrO3 is unfavorably formed from the Sr component in LSCF and the Zr component in YSZ, various thickness of dense SrZrO3 layers were fabricated on the surface of YSZ pellet by applying SrCO3 paste and heat treating at three different temperatures and subsequently the oxygen isotope exchange experiments were performed for the samples. The 18O profiles and associated elemental distribution were determined across the layers by Secondary Ion Mass Spectrometry. Results have revealed that the 18O profiles are found largely deviated from those expected from the bulk diffusion in the homogenized substance particularly in the vicinity of the surface of SrZrO3 and the phase boundaries between SrZrO3 and YSZ.

The concept of a new reversible metal air battery with high cycling capability is based on a porous structure of iron-iron oxide serving as storage of low oxygen activity which is coupled to the negative electrode of a solid oxide fuel / electrolyzer cell via gas diffusion in stagnant atmosphere of a gaseous redox couple. The positive electrode is supplied by air. Such concept does not suffer from the problem of degrading contacts in the storage electrodes caused by volume change of solid phases upon charge and discharge. Basic quantitative reasoning shows that as gaseous redox couple a mixture of hydrogen and water vapor is ideally suited to achieve high performance. Experimental results are presented, which demonstrate the low overall polarization of this kind of storage concept.

Mixed ionic and electronic conducting (MIEC) membranes of Gd-doped CeO2 and Gd-doped SrTiO3 have been employed to generate and separate hydrogen. In this process steam at high temperatures is fed to one side of the MIEC membrane and a hydrocarbon feed or reformate to the other side. Hydrogen is formed through the splitting of steam on the steam side of the membrane. Oxygen is transported through coupled transport of oxygen ions and electrons to the other side of the membrane where it reacts with hydrocarbon or reformate to form products of combustion. Once the residual steam is condensed on the steam side, a feed of pure hydrogen is obtained.

The effect of La doping on conductivity of ZrO2 - Sc2O3 - CeO2 system was studied. The presence of the hysteresis loop was showed and connected with the polymorphic transformation from the ortorhombohedral phase to the cubic phase. 0,5 mol. % La2O3 doping replaces the hysteresis loop in a region of high temperatures. The received results is discussed in borders of the baric model for the ionic conductivity of zirconium oxide which assumes the control character for the influence of the hydrostatic pressure on the diffusion mobility of oxygen ions.

High dislocation density in zirconia systems may significantly affect oxygen ion conductivity. Several processes for introduction of high dislocation density were investigated including ion irradiation. YSZ single crystals were irradiated with Ar+ ions and dislocations were observed by TEM. After heat treatment, high dislocation density was observed in a certain range of depth, and no dislocations were observed in the vicinity of the surface. Conductivity measurements by AC impedance spectroscopy indicated that conductivity improved by 55%.

Ionicity has been raised as an important factor in discussing defect formation in Hf-based oxides. It has been elucidated from our first-principles calculations, that the stability of defects is dominated by Coulomb interactions between charged defects and surrounding ions. For instance, the formation energy of positively charged oxygen vacancies (VO+2) is markedly decreased when they are coupled with substitutional N atoms at O sites, as the nominal charges of N3- are negatively greater than those of the oxygen ions O2-. Our computational results have further revealed that the ionic character of Hf causes generation of a low-lying Si dangling bond level in Si doped HfSiOx. These results suggest that one must take into account the ionicity of the Hf-based compounds, which possess totally different properties from the conventional gate insulator SiO2 in terms of defect formation.

Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) can be used to study the mechanisms and kinetics of electrochemical reactions at solid-solid interfaces. A thin gold film-yittria stabilized zirconia (Au/YSZ) electrolyte interface was used as a model experimental system with a three-electrode configuration. Oxidation and reduction of the sample surface under chemically well-defined experimental conditions were induced. The oxygen ion transport behavior on the Au/YSZ electrolyte interface was analyzed in order to gain a better understanding of the oxygen reduction mechanism and to improve the electrolyte performance. This work focuses primarily on the charge transfer coefficient of oxygen ion transport on the Au/YSZ electrolyte interface as interpreted in terms of kinetic parameters obtained from impedance spectra and cyclic voltammograms as functions of operating temperature. The charge transfer coefficients obtained agreement suggests from the references that the polarization curve is distributed to a two-electron transfer process.

We investigated the bonding-related gases trapped inside the cavities of micromachined silicon test structures that had been sealed by silicon direct bonding or anodic bonding under vacuum conditions. The gas content inside the cavities was analyzed by quadruple mass spectroscopy. The magnitude of the residual gas pressure inside the cavities for different cavity layouts and for various bonding processes was monitored. In cavities bonded by low-temperature silicon direct bonding the residual gases are reaction products originating from the mating silicon surfaces during annealing. Inside the cavities mainly H 2 , H 2 O, and N 2 are found. The total gas pressure is primarily determined by the H 2 component. Cavities sealed by anodic bonding mainly contain O 2 , which originates from mobile oxygen ions inside the bonding glass. The residual gas pressure inside anodically bonded cavities depends neither on the applied bonding voltage nor on the bonding area surrounding each cavity.

The buried oxide (BOX) layers of SIMOX structures produced by oxygen ion implantation are confined between the Si substrate and top Si layer. Their charge trapping properties, as affected by various treatments in the presence or absence of the confining top Si layer, were studied. The BOX of most of the SIMOX samples we have studied contain electron traps related to excess silicon in the form of clusters about 1-4 nm in size. In contrast, unconfined oxides, such as thermally grown SiO 2 films and the so-called equilibrium oxide prepared by oxygen ion implantation to such a thickness that all of the top Si layer is consumed, do not contain these traps. The density of traps with a relatively small capture cross section in confined BOX layers can be reduced by implanting supplemental oxygen into the completed SIMOX structure. However, the traps with relatively large cross section are only slightly affected, despite a significant increase in the oxide thickness. In contrast, traps can be completely eliminated by an oxidizing heat-treatment without measurable additional oxide growth if the structure is unconfined, i.e., the top Si layer is removed. It is suggested that the confinement effect is related to the structure of the noncrystalline BOX layer which is affected by the confining Si layers. This effect stabilizes the traps, particularly those with a large cross section, which are near the Si/BOX interface(s).

This study discusses the sign of the charge of the gas phase species involved in the plasma oxidation of silicon and the oxidation mechanism itself in a system of a type previously reported in which oxidation occurs on a silicon surface facing away from a confined plasma. Based on grid-biasing experiments, it was found that the gas phase oxygen species responsible for oxidation are positively charged, in marked distinction to what has been proposed for plasma anodization processes. From O 18 and Si 30 double-marker experiments, coupled with other information, the oxidation process was found to proceed by oxygen ion transport to the Si-SiO 2 interface with no outdiffusion of silicon being detected

Amorphous InGaZnO (α-IGZO) thin-film transistors (TFTs) are very promising due to their potential use in thin film electronics and display drivers. However, the stability of AOS-TFTs under the various stresses has been issued for the practical AOSs applications. Up to now, many researchers have studied to understand the sub-gap density of states (DOS) as the root cause of instability. Nomura et al. reported that these deep defects are located in the surface layer of the α-IGZO channel. Also, Kim et al. reported that the interfacial traps can be affected by different RF-power during RF magnetron sputtering process. It is well known that these defect states can influence on the performances and stabilities of α-IGZO TFTs. Nevertheless, it has not been reported how these defects are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOI) can be generated by electron attachment in oxygen atom near target surface and accelerated up to few hundreds eV by a self-bias of RF magnetron sputter; the high energy bombardment of NOIs generates bulk defects in oxide thin films and can create the defects of α-IGZO thin films. The a-IGZO TFTs have been fabricated with different dc biases (200 V, 300V, and 400V). Figure 1 shows that the transfer characteristics of the a-IGZO TFTs with a positive bias stress (PBS in (a)), a negative bias stress (NBS in (b)), and a negative bias illumination stress (NBIS in (c)). It is observed that the changes of the transfer characteristics with PBS, and NBS are not depended on different dc biases. However, a huge shift of a threshold voltage on a-IGZO TFTs is observed under NIBS condition. In this study, we have investigated that the NOIs accelerated by dc self-bias were one of the dominant causes of instability in α-IGZO TFTs when the channel layer was deposited by conventional RF magnetron sputtering system. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process to prevent the NOIs bombardment effects and present how much to be improved the instability of α-IGZO TFTs by this new deposition method.

A BaMgAl 10 O 17 :Eu 2+ blue-emitting phosphor was synthesized, and the photoluminescence properties of phosphors annealed in air, nitrogen, and reducing atmospheres were investigated. The photoluminescence intensity of the BaMgAl 10 O 17 :Eu 2+ phosphor annealed in nitrogen atmosphere decreased to a low value and then suddenly increased to more than that of the unannealed sample when the annealing temperature increased. This can be explained by the self-reduction of Eu 3+ and introduced defects. The introduced defects brought by oxygen ions make the crystal structure disturbed and then induce the thermal degradation. The defects can be restricted by a reducing atmosphere.

The resistive switching mechanisms of ZrO 2 memory films are proposed to explain why resistive switching characteristics of Ti/ZrO 2 /Pt device are more stable than those of Pt/ZrO 2 /Pt and Al/ZrO 2 /Pt devices in this study. Different from the Pt/ZrO 2 /Pt and the Al/ZrO 2 /Pt devices, the carrier conduction mechanisms in the Ti/ZrO 2 /Pt device obey space charge limited current theory, which may be caused by the formation of the interface layer between Ti and ZrO 2 . Moreover, the resistive switching mechanisms are proposed to be related to the filament formation/rupture theory and oxygen ion migration. The location where filament formation/rupture takes place should be confined near the interface between Ti and ZrO 2 , leading to the stable resistive switching characteristics and a better endurance performance. During successive resistive cycles at room temperature and 150°C, the fatigue behaviors are observed due to the degradation of both two memory states, which might be related to the transformation of the interface layers between Ti and ZrO 2 and the coalescence of ZrO x clusters.

The electrode dependence of bipolar resistive switching in SrZrO 3 :Cr-based metal-oxide-metal (MOM) structures was investigated. The Pt/SrZrO 3 :Cr/SrRuO 3 structures showed bipolar resistive switching, and the polarities of external bias for set/reset processes were determined by the junction between SrZrO 3 :Cr film and SrRuO 3 electrode. The MOM structure consisting of noble metal electrodes (Pt/SrZrO 3 :Cr/Pt) did not show resistive switching, while the TiO x N y -inserted MOM structure (Pt/SrZrO 3 :Cr/TiO x N y /Pt) exhibited reproducible resistive switching behavior. The results suggest that resistive switching behaviors are related to the formation and annihilation of oxygen vacancies within local conduction paths by electric-field-induced oxygen ion migration.

Variation of lattice constants of Ce 1- xM x O 2-0.5x-δ (M = Gd, Sm, Y; x = 0, 0.1, 0.2) with temperature and oxygen ion vacancy concentration was investigated with X-ray diffraction (XRD) at 600-1000°C under various gas atmospheres. Linear thermal expansion and increase of expansion coefficient with trivalent cation content were observed in every specimen under N 2 and O 2 atmospheres. In N 2 /H 2 /H 2 O gas mixtures, expansion due to generation of oxygen ion vacancies was observed at temperatures higher than 600°C for every specimen. Irrespective of the kinds of trivalent cations, the dependence of lattice constants on 8 was almost linear for the specimen with x = 0.2, whereas bending point was observed for those with x = 0.1 and for pure ceria. The bending point was observed at around 0.1 of 0.5x + 6, which was the total amount of oxygen ion vacancies.