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Solid oxide electrolysis cells (SOECs) have the potential to be highly efficient devices for high-temperature CO2electrolysis. However, commonly used Ni-based cathodes suffer from redox instability under CO/CO2 conditions. La(Sr)Cr(Mn)O3 (LSCM) is a promising alternative due to its coking resistance, but it has poor catalytic activity on CO2reduction. To address this, Ce(Mn, Fe)O2 (CMF) was added as a catalyst to accelerate CO2 adsorption. In this study, the non-touchable coating process by spraying was employed to fabricate the well-decorated embedded CMF on LSCM surface, without complicated pretreatment and infiltration. The performances of the highly decorated electrode surface with CMF nano catalyst were measured at 1123 K, exhibiting a maximum power density of 0.503 W cm-2 in fuel cell mode (H2) and electrolysis performance of 0.835 A cm-2 at 1.5 V in CO2 reduction. This approach shows potential for enhancing the catalytic activity of LSCM cathodes and advancing the development of SOECs for sustainable energy production.

Many studies have been reported for not only efficient production of hydrogen via SOECs but also high performed SOFCs, and La1-x Sr x Ga1-y Mg y O3-δ (LSGM), a substitute for yttria-stabilized zirconia (YSZ) has emerged as a rising candidate for the electrolyte due to its superior ionic conductivity even in intermediate temperature (≤1073K). LSGM has superior ionic conductivity even at intermediate temperatures, allowing for better durability and efficiency at lower operating temperatures. However, there are still challenges with LSGM, such as lower mechanical strength and higher reactivity with electrodes, which make it difficult to manufacture cost-effectively and find compatible materials. Strategies for advanced manufacturing have been developed at KICET, including lowering temperature processing, ultra-thinner self-standing electrolytes, non-touchable electrode coating processing, and optimal microstructure. The innovative activity on recent LSGM-based solid oxide electrochemical devices will be discussed, including achieving outstanding maximum power density and high electrolysis performance.

Logs that record system information are managed in anomaly detection, and more efficient anomaly detection methods have been proposed due to their increase in complexity and scale. Accordingly, deep learning models that automatically detect system anomalies through log data learning have been proposed. However, in existing log anomaly detection models, user logs are collected from the central server system, exposing the data collection process to the risk of leaking sensitive information. A distributed learning method, federated learning, is a trend proposed for artificial intelligence learning regarding sensitive information because it guarantees the anonymity of the collected user data and collects only weights learned from each local server in the central server. In this paper, we executed an experiment regarding system log anomaly detection using federated learning. The results demonstrate the feasibility of applying federated learning in deep-learning-based system-log anomaly detection compared to the existing centralized learning method. Moreover, we present an efficient deep-learning model based on federated learning for system log anomaly detection.

An enhanced CO2 electrolysis current density of 2.20 A cm−2 @ 1.5 V at 1123 K is achieved for LSFM electrodes using Fe catalyst rather than Ru, Ni, and Co catalysts.

High temperature electrolysis is a promising option for carbon-free hydrogen production and huge energy storage with high energy conversion efficiencies from renewable and nuclear resources. Over the past few decades, yttria-stabilized zirconia (YSZ) based ion conductor has been widely used as a solid electrolyte in solid oxide electrolysis cells (SOECs). However, its high operation temperature and lower conductivity in the appropriate temperature range for solid electrochemical devices were major drawbacks. Regarding improving ionic-conducting electrolytes, several groups have contributed significantly to developing and applying LaGaO3 based perovskite as a superior ionic conductor. La(Sr)Ga(Mg)O3 (LSGM) electrolyte was successfully validated for intermediate-temperature solid oxide fuel cells (SOFCs) but was rarely conducted on SOECs for its high efficient electrolysis performance. Their lower mechanical strengths or higher reactivity with electrode compared with the YSZ electrolysis cells, which make it difficult to choose compatible materials, remain major challenges. In this field, SOECs have attracted a great attention in the last few years, as they offer significant power and higher efficiencies compared to conventional YSZ based electrolysers. Herein, SOECs using LSGM based electrolyte, their applications, high performance, and their issues will be reviewed.

(La,Sr)TiO3 has been investigated as a promising anode material for solid oxide fuel cells (SOFCs) owing to its high electronic conductivity and superior phase stability. However, the low catalytic activity of (La,Sr)TiO3 materials is a major obstacle to the application of SOFCs. Exsolution has emerged as an effective strategy to overcome the low catalytic activity of (La,Sr)TiO3 materials. In this work, Ni-doped A-site-deficient La0.4Sr0.4TiO3-δ (LST) (i.e., La0.4Sr0.4Ti0.94Ni0.06O3-δ; LSTN) with in-situ exsolved Ni nanoparticles (NPs) was developed and the effects of exsolved Ni NPs on H2 oxidation was investigated. The doped Ni was exsolved and formed NPs on the LSTN surface under reducing conditions. Owing to the high catalytic activity of the exsolved Ni NPs, the SOFC with LSTN-Ce0.9Gd0.1O2-δ (GDC) yielded a maximum power density of 0.46 W cm−2 at 850°C, 91% higher than that of the cell with LST-GDC, as well as high long-term and redox stability. Furthermore, density functional theory calculations revealed that the adsorption and dissociation of H2 were more favorable for exsolved Ni NPs than for pure Ni owing to the more positively charged surface of the exsolved Ni NPs in the LSTN. These results demonstrated that exsolution is an effective method for improving the electrocatalytic activity of perovskite (La,Sr)TiO3 materials.

Solid oxide fuel cells (SOFCs) have been gaining increased attention in the energy sector. Commonly, yttria-stabilized zirconia is widely employed as commercial electrolyte, however, resulted in drawbacks such as high-temperature operating and low conductivity which negatively affect the durability and efficiency. Thus there are many efforts to find high-ionic conductors. From the point of manufacturing, the major difficulty of LaGaO3-based electrolyte as a high-ionic conductor is its incompatibility with commercial Ni-based anodes during high-temperature processes as well as operating. Several interlayers have been introduced to prevent the reaction between LaGaO3-based electrolyte and Ni-based anode. In this study, we investigate the optimal thickness of the La-doped CeO2 (LDC) interlayer by the screen-printing method using La0.9Sr0.1Ga0.8Mg0.2O3-δ for the commercial electrolyte supported SOFCs. As a result, the superior power performance of 2.2 W·cm−2 at 1123 K is achieved through the optimized LDC thickness of 20 μm through not lab-scaled but commercial ceramic manufacturing processing.

O estudo tem por objetivo investigar o nível de conhecimento dos profissionais de marketing em relação a finanças e, adicionalmente, analisar como os profissionais da área analisam e mensuram a performance dos investimentos de marketing, para contribuir com o objetivo de maximização do retorno. Foi elaborado uma survey aplicada à profissionais da área marketing, com a obtenção de 27 respondentes para a análise final. Com base nos resultados, é possível verificar que mesmo com a importância da análise dos investimentos em marketing em termos financeiros, os profissionais da área possuem dificuldades para a mediação dos retornos dos investimentos, sugerindo a necessidade de uma melhor preparação e alinhamento com a área de finanças.

In this study, LSM-YSZ composite cathodes were analyzed by changing the firing temperature, composition, and operating temperature to determine the contribution of each step of the oxygen reduction reaction (ORR). The overall resistance of the cathode reaction was characterized by fitting the AC impedance spectra with an equivalent circuit model. It was found that initial reactions of ORR (dissociative adsorption) are the main rate-determining step (RDS) regardless of operating or sintering temperature, while reactions on LSM surface become the main RDS when the ratio of LSM catalysts has a relatively small proportion. The [LSM-YSZ]5:5 cathode fired at 1100 °C showed the best microstructure and lowest resistance in the ORR at an operating temperature of 700 °C (RHF: 0.18 Ωcm2, RMF: 0.20 Ω cm2, RLF: 0.25 Ωcm2, Rcathode: 1.14 Ωcm2). This demonstrates the potential use of LSM-YSZ cathodes for IT/LT-SOFC without the use of expensive materials, such as LSCF and BSCF.

In this study, the electrical conductivity of SmBaCo2O5+d (SBCO) is measured and analyzed with respect to the microstructure of the analyzed samples. The microstructure is influenced by the sintering temperature and by the precise composition of the composite cathode. Difference in the electrical conductivity at different applied current is investigated. The value of the electrical conductivity of SBCO sintered at 1150 °C was about 1024 S/cm at 600 °C, which was the highest compared to other samples sintered at lower temperatures. The electrical conductivities of porous microstructural SBCO sintered at 1150 °C with an addition of 10 wt% carbon black and of a composite cathode comprised of SBCO and Ce0.9Gd0.1O2 (CGO91) at a ratio of 1.9:0.1 were 256 and 525 S/cm at 600 °C. The electrical conductivities of SBCO samples increase when relatively low currents are applied. This trend can be observed at all pure SBCO and samples mixed with carbon black. However, these properties are not found in composite cathodes comprised of SBCO and CGO91.

Conductive susceptors are necessary for heating non-conductive materials in induction heating systems. Susceptor materials should have sufficient electrical conductivity and thermal/chemical stability under a range of environmental conditions. However, many susceptor materials oxidize in high-temperature environments, resulting in degradation and poor durability. Here, we used intermetallic MoSi2 ceramics as a susceptor material and designed a cylindrical susceptor to apply to rapid high-temperature induction heating in an oxidizing environment. MoSi2 was prepared by self-propagating high-temperature synthesis (SHS), and then used to fabricate cylindrical susceptors by slip casting. The optimal thickness of the susceptor was controlled by modelling. A MoSi2-based cylindrical susceptor with SiO2 protective layer showed higher heating rate (4.2–26.8 °C/s at 0.5–2.5 kW) than a commercial rod-type susceptor (7.7–13.6 °C/s at 1.0–2.5 kW) of the same material. In addition, our susceptor endured high temperatures below 1700 °C and severe thermal cycle (700–1600 °C, heating for 2min and cooling for 1min) during 36 cycles. In general, these results demonstrate that the MoSi2-based susceptor can be applied to a rapid induction heating furnace that can be used in air at a high temperature of 1600 °C (equal to the available temperature of a commercial graphite susceptor in H2).

The durability of catalysts in fuel cells is a longstanding issue that needs to be resolved. Catalyst stability of the fuel cell has always been a problem, studies are underway to address them. Herein, to address this issue, we synthesize a hybrid structure consisting of SP carbon (SP) as the graphitic carbon and TiO2 as the metal oxide using a microwave method for use as a support for Pt nanoparticles. Anatase TiO2 and Pt nanoparticles with sizes of ~5 and 3.5 ± 1.4 nm, respectively, are uniformly dispersed on a modified graphitic SP carbon support (Pt-TiO2-SP). This supported Pt catalyst exhibits significantly improves durability in the oxygen reduction reaction (ORR). Furthermore, the Pt-TiO2-SP carbon hybrid catalyst manifests superior electrocatalytic stability and higher onset potential in ORR than those exhibited by Pt-SP carbon without TiO2. Pt-TiO2-SP exhibits an activity loss of less than 68 mV after 5000 electrochemical cycles, whereas an activity loss of ~100 mV is observed for Pt-SP carbon in a stability test. These results suggest that the strong metal–support interaction in TiO2-supported Pt catalyst significantly enhances the activity of Pt nanocatalyst.

The solid oxide membrane (SOM) process is an environmentally friendly and innovative technology that can produce valuable metals directly from their oxides. In the SOM process, a yttria-stabilized zirconia (YSZ) tube is normally immersed the molten salt containing dissolved metal oxides and oxygen anions that move to the SOM tube where they are reduced without any emission. However, the YSZ phase transition and yttrium dissolution by the reaction with the flux reduce the SOM stability and lifetime. Here, we investigated the effect of powder characteristics on YSZ stability in the SOM electrolysis environment. Thus, powder with good formability such as high flowability and tap/untap density showed a 2% decrease in electrical conductivity, but a 17% decrease in low formability powders. The cause of the degradation is the penetration of salt ions into the lattice and the elution of yttrium ions, which results in a phase transition.

One of the important challenges with a bifunctional electrocatalyst is reducing the large overpotential involved in the slow kinetics of the oxygen evolution reaction (OER) and oxygen reduction rea...

La-doped strontium titanates have attracted much interest as promising reliable ceramic anodes for solid oxide fuel cells (SOFCs) owing to their superior redox-stability. Moreover, recent studies demonstrated that A-site deficiency of the La-doped SrTiO3 perovskite could effectively promote conductivity and catalytic activity, simultaneously. In this study, we developed the LST44-Ce0.9Gd0.1O1.95 (GDC) composite anodes, and investigated their electrochemical performance and redox stability on La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) electrolyte-based SOFCs. During galvanostatic long-term stability tests combined with in situ redox cycles, power out-put performance of the LST44-GDC employed SOFC was initially increased by ∼53% to 0.26 W cm−2 and maintained the high performance over 350 h at 800 °C. Analysis of the accumulated electrochemical impedance spectra during the long-term stability test showed that the electrochemical activity of the LST44-GDC anode was promoted at the initial redox cycling. Consequently, this study demonstrates that A-site deficient LST44-GDC is a promising material as an efficient and redox stable SOFC anode.

For the Fundamental studies on the phase stability of YSZ, we tried to approach the detailed influences of practical conditions through various hypotheses. The phase stability of cubic and tetragonal yttria-stabilized zirconia (YSZ) was studied in the specific electrochemical conditions of current loading and molten salt flux. The degradation of electrochemical performance in the cubic phase occurred more easily than in the tetragonal phase because of yttrium elution in the lattice. The fully stabilized cubic phase showed high electrical performance as an oxide ion-conducting electrolyte, but phase decomposition occurred more easily under applied currents or chemical loading conditions than for the partially stabilized tetragonal phase. When YSZ reacted with a molten salt fluoride flux in solid oxide membrane (SOM) processing, which is used for direct metal reduction, and high-temperature electrolysis in the molten salt, the electrical conductivity of cubic YSZ was decreased by ~37%, while that of tetragonal YSZ showed no change. Our findings have important implications for the use of YSZ as an oxygen conductor in various electrochemical devices.

Although numerous perovskite oxides can enhance the electrochemical activity via exsolved metallic nanoparticles on the surface, most of them can only be applied as catalysts in a reducing atmosphere. These nanoparticles cause serious performance degradation in oxidizing conditions due to the formation of low-conductive metal oxides. This poses a big challenge to the design of highly active catalysts of electrochemical devices, especially for symmetrical solid oxide cells. Herein, based on the strategy of exsolved metallic nanoparticles in A-site deficient perovskite, a unique and simple method is demonstrated for the synthesis of Ru/RuO2 nanoparticles on the surface of perovskite oxide via in situ growth. The electrode material (La0.75Sr0.25)0.9Cr0.5Mn0.45Ru0.05O3−δ (LSCMR) is designed through careful choice of composition and the core idea is to make use of the exsolved nanoparticles concept applied for the first time at both hydrogen electrode and oxygen electrode for symmetrical solid oxide cells. Inspired by exsolved Ru and RuO2, the surface-decorated LSCMR exhibits significantly enhanced electrochemical activity for both H2 and O2, respectively, accompanied by high redox long-term stability. Moreover, simple, low-cost, and environmental-friendly synthesis of Ru/RuO2 nanoparticles on the substrate of typical perovskites is realized with this in situ growth approach.

In this study, the chemical states of a powder type and an impregnated type of the La0.4Sr0.6Ti0.8Mn0.2O3±d (LSTM) oxide system were investigated along with its electrical conductivities in order to apply these materials as alternative anode materials for high temperature-operating Solid Oxide Fuel Cells (HT-SOFCs). The Ni/8YSZ samples with LSTM impregnated into the pores created by partially removing nickel, Ni/8YSZ (Ni (R)/8YSZ), showed much higher electrical conductivity values than those of unimpregnated Ni/8YSZ (Ni (E)/8YSZ) samples under dry H2 fuel condition. Reduction of Mn4+ to Mn3+ was observed when LSTM was reduced. Additional reduction properties of Mn2+ from Mn3+ and satellite peaks were found when impregnated LSTM was coated onto a Ni/8YSZ substrate. The reduction of the charge state of Ti contained in LSTM showed the same behavior as the reduction property of Mn. However, a satellite peak identified as metal Ti was only observed when impregnated LSTM was coated on a selectively Ni-removed Ni/8YSZ (Ni (R)/8YSZ) substrate.

In this study, the microstructural and electrochemical properties of linear type nanofibers obtained by adding SmBa0.5Sr0.5Co2O5+d (SBSCO) layered perovskite oxide were investigated for use as cathode materials in a low temperature-operating solid oxide fuel cell. Linear type SBSCO fiber and Ce0.9Gd0.1O2−d coated SBSCO-fiber were fabricated using the electrospinning process. It was confirmed that the area specific resistance (0.75 Ω cm2) of the obtained SBSCO-fiber cathode was much lower than that (1.25 Ω cm2) of a powder-type SBSCO cathode at 550 °C. The result shows that the SBSCO fiber cathode exhibits lower polarization resistance in low temperature ranges than the powder SBSCO cathode materials do. A significantly lower activation energy (0.76 eV) was observed in fiber SBSCO cathode than in the nanostructured La0.8Sr0.2Co0.2Fe0.8O3−d ones which were used as control at 1.53 eV.

Direct CH4-fueled solid oxide fuel cells (SOFCs) have been studied for a few decades, but carbon depositions on the Ni-based anodes are still remained as a major problem. In order to enhance coke tolerances and durability of SOFCs, La2Sn2O7 nano-powders are prepared by co-precipitation. The SOFCs with the different amounts of the La2Sn2O7 nano-powders in the Ni-GDC anodes are tested under dry CH4, and the 0.3 wt.% La2Sn2O7-Ni-GDC (0.3LNG) anodes show the highest cell performances of all anodes. The maximum power density of the cell is approximately 0.55 W cm−2 at 650 °C. The durability of the 0.3LNG cell is significantly enhanced without any carbon formations, showing approximately 0.69 V over 600 h at 0.3 A cm−2, whereas the conventional Ni-GDC cell is stopped only after 90 h. It suggests that the 0.3LNG is a promising anode material to enhance coke-tolerances and durability of direct-methane fuel cells.

Electric vehicles (EVs) require high operating voltages as well as high-capacity batteries. One candidate material that has received a great deal of attention is the nickel-substituted “high-voltage” spinel LiMn1.5Ni0.5O4, which offers the advantages of both higher capacity and higher operating voltage than spinel LiMn2O4. These features, along with the relatively benign constituent elements, have made this material a top choice for the next generation of high-power batteries. In this study, LiMn1.5Ni0.5O4−δ materials were synthesized by a microwave-assisted hydrothermal method. Analyses show that microwave irradiation enables the tuning of the Mn3+ concentration, which is related to the degree of disorder and enhances the electrochemical performance. However, with increasing synthesis time, the material limit of the elastic strain was exceeded, and the structure became morphologically unstable, which deteriorated the electrochemical performance. Thus, further efforts are necessary to improve its intrinsic stability. The LiMn1.5Ni0.5O4−δ cathode active material may be suitable for the rapid charging of electric vehicle batteries.

In this study, the phase synthesis and electrochemical properties of A/A//A///B2O5+d (A/: Lanthanide, A//: Ba, and A//: Sr) layered perovskites in which Pr and Sm were substituted at the A/-site were investigated for cathode materials of Intermediate Temperature-Operating Solid Oxide Fuel cells (IT-SOFC). In the PrxSm1-xBa0.5Sr0.5Co2O5+d (x = 0.1–0.9) systems, tetragonal (x &lt, 0.4) and orthorhombic (x ≥ 0.5) crystalline structures were confirmed according to the substitution amount of Pr, which has a relatively large ionic radius, and Sm, which has a small ionic radius. All of the layered perovskite oxide systems utilized in this study presented typical metallic conductivity behavior, with decreasing electrical conductivity as temperature increased. In addition, Pr0.5Sm0.5Ba0.5Sr0.5Co2O5+d (PSBSCO55), showing a tetragonal crystalline structure, had the lowest conductivity values. However, the Area-Specific Resistance (ASR) of PSBSCO55 was found to be 0.10 Ωcm2 at 700 °C, which is lower than those of the other compositions.

This work was supported by the Technology Innovation Program (grant no. 20182010600400) funded by the Ministry or Trade, Industry & Energy (MI, Korea). Support was also provided by the Technology Innovation Program (Grant Nos. 20004963) funded by Ministry of Trade, Industry and Energy (MOTIE) of Korea. We also thank Korea Institute of Ceramic Engineering and Technology (KICET) internal program (KPP20003) for support. The electrochemical reduction of CO2 using a highly efficient solid oxide electrolyzer could be considered an alternative to the advanced utilization of CO2. The La(Sr)Cr(Mn)O3 (LSCM) perovskite oxide has previously been examined as a promising ceramic cathode material for application in a CO2 solid oxide electrolyzer at high temperatures. However, LSCM suffers from low electrocatalytic activity towards CO2 reduction. In this study, a modified LSCM-based cathode material is fabricated by co-infiltrating Pd metal and Ce0.8Gd0.2O1.9 (GDC) nanoparticles on the surface of the LSCM scaffold. Structural characterization and electrochemical analysis of the high-temperature CO2 electrolysis procedure are conducted for various CO/CO2 mixtures and at different operating temperatures. The enhanced electrocatalytic activity of the Pd-GDC co-infiltrated LSCM cathode compared to LSCM is attributed to the increased numbers of active triple phase boundaries and surface oxygen vacancies resulting from the co-infiltration of Pd-GDC nanoparticles on the LSCM cathode. Postprint Postprint

A key obstacle in reducing temperature loss is ohmic loss, which could be lowered by the use of thin electrolytes in electrochemical devices and thus various thin film processing methods have attracted much attention for applications in the SOFC market. Doped stabilized zirconia, Zr1−xMxO2−δ (M = Y, Sc), thin films were successfully deposited on a porous Ni-YSZ substrate via a commercial 10 kW EB-PVD system. The highly conductive and dense Zr1−xMxO2−δ (M = Y, Sc) thin films could be obtained by optimizing the distance (20–40 cm) between the substrate and target, angle (cos α, α = 0.19π–0.36π) for deposition area and substrate temperature (600–950 °C). Pseudo-cubic phase zirconia, with a preferential crystalline growth (111) and a unique columnar morphology, was observed with a fairly good value of conductivity; ScSZ and YSZ films had conductivities of 0.23 and 0.11 S cm−1 at 900 °C in air. This was achieved on the films which were prepared with proper geometric factors for physical deposition and with a substrate temperature of 950 °C. Finally, the YSZ and ScSZ electrolytes, prepared by EB-PVD, were applied on a solid oxide fuel cell with a Ni-YSZ anode and LSM cathode, which showed 1 W cm−2 of power density under 0.75 V at 900 °C.

A highly stable electrode material of Ruddlesden–Popper structure, La1.2Sr0.8Mn0.4Fe0.6O4 (RPLSMF), is prepared from La0.6Sr0.4Mn0.2Fe0.8O3 (LSMF) perovskite by in situ annealing in flowing H2 at the operation temperature of solid oxide fuel cells. The crystallinity, morphology, and oxidation states of each element and electrochemical properties of RPLSMF are characterized. Doping Mn into the B-site of RPLSMF improves the phase stability of the structure in H2 to prevent formation of La2O3. The XPS results also suggest that improved phase stability promotes formation of Fe2+/3+ pairs that facilitate fuel oxidation by redox coupling. Additionally, during phase transition to RPLSMF, metallic Fe nanoparticles form, which enlarge H2 chemisorption and oxidation sites. Consequently, RPLSMF exhibits outstanding and stable electrochemical activity with a maximum power density of 0.72 W cm−2 at 1073 K when used as an anode material in LSGM electrolyte-supported cells. As the phase transition between the RPLSMF and LSMF is reversible under a redox environment, RPLSMF/GDC is applied as an electrode in the symmetrical cell of RPLSMF-GDC/LSGM/LSMF-GDC. It exhibits a substantial power density of 0.64 W cm−2 with a total polarization resistance of 0.51 Ω cm2.

A molecular dynamics simulation was used to investigate the structural and transport properties of a (Ba0.5−xSrx)La0.5InO3−δ (x = 0, 0.1, 0.2) oxygen ion conductor. Previous studies reported that the ionic conductivity of Ba-doped LaInO3 decreases because Ba dopant forms a narrow oxygen path in the lattice, which could hinder the diffusion of oxygen ions. In this study, we reveal the mechanism to improve ionic conductivity by Ba and Sr co-doping on an La site in LaInO3 perovskite oxide. The results show that the ionic conductivity of (Ba0.5−xSrx)La0.5InO3−δ increases with an increasing number of Sr ions because oxygen diffusion paths which contain Sr ions have a larger critical radius than those containing Ba ions. The radial distribution function (RDF) calculations show that the peak heights in compositions including Sr ions were lower and broadened, meaning that the oxygen ions moved easily into other oxygen sites.