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Sealing performance and chemical compatibility of SrO–La 2 O 3 –Al 2 O 3 –SiO 2 glass sealants with bare and Mn–Co spinel coated SUS430 ferritic alloys are investigated. The low–SrO glasses (≤40 mol%) show good wettability and adherence to the bare SUS430 alloy due to their lower viscosity and negligible reactions with the alloy. The high–SrO glass (e.g. 45 mol%) exhibits higher viscosity and more serious reactions with the bare SUS430 alloy. The formation of SrCrO 4 with higher CTE causes obvious delamination and dramatic oxidation of the alloy at the glass/alloy interface. In contrast, Mn–Co spinel coating has good compatibility with both SrO–La 2 O 3 –Al 2 O 3 –SiO 2 glasses and Fe–Cr ferritic alloy. Moreover, the Mn–Co spinel coating on the alloy can effectively restrain the diffusion of Fe and Cr and the reactions between the glasses and the alloy. Due to the ameliorated interfacial microstructure, sealing performance can be improved by applying the Mn–Co spinel coating on SUS430 alloy, especially for the bonded couple with high–SrO glass.

SrO–La 2 O 3 –Al 2 O 3 –SiO 2 glasses with different SrO content are prepared and their stability in high temperature air and steam are investigated. All glasses are stable during 1000 h test at 800 °C in air. Nevertheless, the high–SrO glasses (≥40 mol%) are devitrified on the surfaces when they are treated at 850–900 °C in air or exposed to steam. 29 Si magic–angle–spinning nuclear magnetic resonance study reveals weaker connections between [SiO 4 ] tetrahedral units and increased micro–heterogeneity of glass networks with increasing SrO content, which should be responsible to the lower stability of the high–SrO glasses. It indicates that a careful control of SrO content is necessary to develop stable SrO–La 2 O 3 –Al 2 O 3 –SiO 2 glass sealants for solid oxide fuel cells and solid oxide electrolysis cells.

In order to restrain the decomposition and conductivity degradation of perovskite-type conductive material in the presence of chromia, manganese oxide modification of lanthanum strontium cobaltite has been studied. La 0.7 Sr 0.3 CoO 3− δ (LSC) and MnO 2 -modified LSC coatings are applied onto Ni–Cr alloy and exposed to long-term oxidation text to examine their chemical stability. In a LSC coating, chromium species migrating from the Ni–Cr alloy could induce the decomposition of LSC and produce SrCrO 4 and Co–Cr spinel oxides. In contrast, in the MnO 2 -modified LSC, Sr is stable and the low-conductivity phase SrCrO 4 phase is rarely seen even the coated alloy has gone through 1000 h of oxidation tests at 800 °C. It highlights that MnO 2 modification could greatly improve the stability of LSC under Cr-rich conditions. The study of solid state reactions reveals that the influence of MnO 2 is mainly due to the reaction between MnO 2 and LSC, instead of the direct reaction between MnO 2 and chromium oxides.

The grain boundary plays an important role in the electrical behaviors of solid oxide electrolytes for solid state fuel cells. To reveal the relationship between the structure and the ionic conductivity of grain boundary, the conductive properties of {1 1 1} and {1 1 0} twist grain boundaries in 8 mol% yttria-stabilized zirconia have been examined. These boundaries have a series of Σ values defined by the coincident site lattice model. It has been found that the activation energy of {1 1 1} twist grain boundary increases and then decreases with the Σ value, while that of the {1 1 0} boundary shows an opposite trend. It is suggested that the properties can reflect the balance of the effects of lattice mismatch on the diffusion ability of oxygen vacancies and the segregation of oxygen vacancies and Y3+ ions. Therefore, the properties in polycrystalline electrolyte can be adjusted by controlling the grain boundary structures.

Low-temperature-sintered MnCo 2 O 4 –MnO 2 coatings have been prepared on pre-oxidized SUS430 ferritic alloy by slurry coating. The effect of pre-oxidation treatment before slurry coating is then investigated. Microstructural and electrical characterizations show that 25 h of pre-oxidation at 800 °C could significantly improve the oxidation resistance of the coated alloy and effectively inhibit the increase in area-specific electrical resistance during long-term oxidation. These effects can be explained by the interfacial reactions between the coating and the pre-oxidized alloy during sintering and oxidation tests. Furthermore, this study suggests that the dense reaction layer at the coating-alloy interface could be the key to improving the oxidation resistance of metallic interconnects with low-temperature-sintered spinel coatings.

Six interatomic potentials based on Buckingham potential form for yttria-stablized zirconia have been critically assessed by predicting lattice constants, dielectric constants, and elastic properties using the mean-field approach. The content of Y2O3is set to the range from 8 to 24 mol%. It has been found out that no potential can reproduce all the fundamental properties. Taking all the simulation and comparison results into consideration, the potential of Butler (1981) displays the highest fidelity, and the potential of Lewis (1985) shows the widest range of applicability.

To reduce the sintering temperature of spinel coatings to a safe temperature for Fe–Cr ferritic alloys, an MnCo2O4–MnO2 bicomponent coating has been prepared on SUS430 ferritic alloy by slurry coating, followed by air sintering at a temperature of 800 °C. The resultant coating is stable during cyclic oxidation tests and is effective at improving the oxidation resistance of SUS430 alloy. The area-specific resistance of coated samples remains nearly constant during long-term oxidation at 800 °C and is less than 6 mΩ cm2 even after oxidation for 1000 h. These results indicate that the low-temperature sintered MnCo2O4–MnO2 coating is a promising protective material for Fe–Cr ferrite alloys, especially SUS430, which are seriously oxidized at temperatures ≥850 °C.

Microstructural evolution in a CeO2-Gd2O3 system at atomic and nanoscale levels with increasing Gd concentration has been comprehensively investigated by transmission electron microscopy. When the Gd concentration was increased from 10 to 80 at.%, the phase transformation from ceria with fluorite structure to solid solution with C-type structure was not a sudden change but an evolution in the sequence of clusters, domains, and precipitates with C-type structure in the fluorite-structured matrix. Moreover, the ordering of aggregated Gd cations and oxygen vacancies in these microstructural inhomogeneities developed continuously with increasing Gd concentration. This microstructural evolution can be further described based on the development of defect clusters containing Gd cations and oxygen vacancies.

Pt-CeOx/C (1.5

Pt on ceria (CeOx) particles supported on carbon black (CB) were synthesized using the combined process of hot precipitation and impregnation methods. During 30 cycles of cyclic voltammetry pre-treatment in the potential ranging from −0.2 to 1.3 V (V vs. Ag/AgCl), it was observed that a small amount of CeOx, which consisted of the interface region between Pt and CeOx, remained on Pt particles. Other free CeOx particles were dissolved into H2SO4 aqueous solution. To develop the Pt-CeOx/CB catalyst, the surface chemical states, the net chemical composition, morphology and electrochemical behavior in H2SO4 aqueous solution were characterized. Our microanalysis and electrochemical analysis indicate that the active CeO2 with high specific surface area provides the continuous amorphous cerium oxide (Ce3+ ,C e 4+) layer with pores on the surface of Pt particles. It is concluded that the amorphous cerium oxide layer on Pt inhibits the oxidation of Pt surface and contributes to enhancement of the activity on Pt cathode. The single cell performance was also improved using the Pt-CeOx/CB cathode. Based on all data, it is expected that the design based on characterization of the interface between Pt and small amount of amorphous cerium oxide layer could help in preparation of more active Pt catalyst.

Nanosized incubational domain was observed in 10 at.% gadolinium-doped ceria (GDC) using high-resolution transmission electron microscopy. Dislocations were extensively observed in 10 at.% GDC instead of heavily doped 25 at.% GDC. By Fast Fourier Transform and Inverse Fast Fourier Transform analysis, it was noticed that the incubational domain existing in 10 at.% GDC has different lattice spacing and orientation from the neighboring ceria matrix. Furthermore, dislocations were usually observed in the interface region between the incubational domain and the ceria matrix. Based on experimental results, the formation mechanism of dislocation associated incubational domain in lightly gadolinium-doped ceria is rationalized.

Dense doped ceria films are promising candidate electrolytes for solid oxide fuel cells (SOFCs) operated at intermediate temperature (∼ 500 °C). In this work, detailed microstructural features of Gd-doped ceria (GDC) electrolyte film supported by Ni-GDC cermet anode were studied. Formation of inhomogeneous microstructures in the GDC film was observed, which was enhanced in the region near the film/anode interface due to the Ni diffusion from the anode. Then, the mechanism by which Ni affects the microstructure was explained by computer simulation of formation and development of defect clusters. © 2010 Elsevier B.V. All rights reserved.

Nano-sized domains have been widely observed in rare-earth-doped ceria, but their structure model remains unclear. In this work, based on the study of high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) of Gd-doped ceria, the structure model of the domains was constructed by a combination of defect clusters with oxygen vacancy chains. Then, the SAED patterns were simulated using this structure model. The simulated results are consistent with the observed SAED patterns.

Defect clusters in several rare-earth-doped ceria (doped with Y, Sm, Gd, Dy and Yb) containing up to four oxygen vacancies and eight dopant cations have been simulated and compared. In all doped ceria systems, the binding energy of the clusters increases with increasing cluster size and the oxygen vacancies tend to form curved chains in the clusters. Moreover, the capability of the growth of defect cluster is affected by dopant type, which can explain the dopant type dependency of domain development with increasing doping concentration in heavily doped ceria.

The microstructure and conductivity property of Ca-doped CeO2 were studied in a wide range of dopant concentrations (from 5 to 50 at.%). Through detailed transmission electron microscopy and X-ray photoelectron spectroscopy investigations, we determined the secondary phase besides the doped ceria, clarified the solubility limit for the dopant and specified the reduction behavior of CeO2 induced by the Ca doping and the associated reduction product. The influences of the microstructures on the ionic conductivity of Ca-doped CeO2 are discussed, from which the optimal doping level of Ca is suggested.

Defect clusters in Gd-doped ceria containing up to four oxygen vacancies and eight dopant cations have been simulated by the Mott–Littleton two-region approach. With increasing cluster size, the magnitude of the binding energy of the clusters increases so that the clusters become more and more stable. Moreover, the oxygen vacancies tend to form curved chains in the clusters, and the adjacent oxygen vacancies are preferentially separated by /2 in the clusters containing more than three oxygen vacancies. It is suggested that the structure of the nano-sized domains that have been reported in heavily doped ceria can be described as an aggregation and combination of these clusters.

We demonstrate a systematic investigation on the microstructure of the Ca-doped ceria affected by different dopant concentrations and calcination temperatures. It has been shown that nanopowders of Ca-doped ceria have been successfully prepared in a broad dopant concentration region from 5 at.% to 70 at.%. By using various microstructure analysis techniques, the secondary phase has been determined, and the solubility of Ca in ceria has been realized to be less than 20 at.%. It has been also found that the calcination temperature greatly affects the grain growth of the calcined powders, and high temperature calcination treatments would cause lattice relaxation and lead to precipitations, based on which proper calcination conditions are suggested.

Nano-sized domains were studied systematically in 10-30 at.% Gd-doped ceria. By using energy filtering transmission electron microscopy, it was observed that Gd cations could segregate in the domains. Due to the requirement of electrical neutrality, oxygen vacancies may also segregate into the domains with the dopant cations. Through study of electron energy loss spectroscopy, the local ordering of oxygen vacancies in the domains was further confirmed. Furthermore, the nano-sized domains and the local ordering develop with increasing doping concentration. Based on the experimental results, the formation mechanism of the domains and their effect on the ionic conductivity are discussed.

Well dispersed Ce 1− x Tb x O 2− δ nano-powders were synthesized by using the carbonate coprecipitation method in an entire compositional range of 0⩽ x ⩽1, which allowed the preparation of highly dense pellets by sintering at 1673 K and the systematical study of the electrical conductivity in such a wide compositional range. It was found that the conductivity increased with increasing Tb concentration except that of x =0.80. Secondary phase were observed by using X-ray diffraction in the samples with x ⩾0.80, which might have negative impact on the conductivity of the samples.

The electrical conduction and microstructure in Y-doped ceria and Ho-doped ceria were investigated. Visible differences between the two doped ceria were observed. The plots of conductivity of Y-doped ceria are well fit to the Arrhenius behavior, while curvature and kinks were observed on the plots of Ho-doped ceria. Such deviation from the Arrhenius behavior could be related to the existence of precipitates in Ho-doped ceria. It indicates that the electrolytic conductivity of doped ceria could be significantly influenced by microstructure features.

A considerable interest has been shown in the application of doped ceria (CeO2) compounds for “intermediate” (300–500 °C) temperature operation of solid oxide fuel cells. The microdomains with ordered structure of oxygen vacancy were observed in the microstructure of the M-doped CeO2-sintered bodies (where M: Gd, Y, and Dy). We have previously shown that the conductivity of doped CeO2-sintered bodies was lower when the sintered body contained large microdomains within grains. As a consequence of this observation, we have examined the grain size dependence and dopant content on conductivity in specimens where we adjust the microdomain size and a degree of oxygen vacancy ordering in the microdomains by controlling the microstructure. The microdomain size control in Dy-doped CeO2 specimens was obtained by combining pulsed electric current sintering and conventional sintering. Using these techniques, we were able to improve the conductivity in Dy-doped CeO2 specimens to a point where it became comparable to that of the more conventional Gd-doped CeO2 specimens. It is concluded that by combining ultimate high-resolution analysis of these nanostructures with the adjusting processing route design, it is possible to further develop these materials in CeO2-doped fuel cell application.

Ce1-xTbxO2-delta nano-powders have been successfully synthesized by using the ammonium carbonate coprecipitation method in an entire compositional range of 0 = 0.7. TEM observation indicated that the secondary phase could have a superstructure formed by a structural modulation of the fluorite structure.

The microstructures of Ce1-xTbxO2-delta (0-10

The microstructures and electrolytic properties of YxCe1-xO2-x/2 (x = 0.10-0.25) electrolytes with average grain size in the range 90 nm-1.7 mu m were systematically investigated. Through detailed transmission electron microscopy characterization, nanosized domains were observed. The relationship of the domains, the doping level and grain sizes were determined, and their impacts on the electrolytic properties were systematically studied. It was found that the formation of domains has a negative impact on the electrolytic properties, so that electrolytic properties can be adjusted through careful control of domain formation, doping level and grain size. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Carbon monoxide (CO) is a significant air pollutant produced in incomplete oxidation of carbon in combustion. From the viewpoint of environmental protection, it is important that the concentration of CO gas is lowered in air. Catalysis is proving to be an effective route for removing this pollutant. Therefore, a design of nano-structured catalysts with high efficiency is required. In the present work, we focus on a development of nano-size CuOx-CeO2 catalysts for CO oxidation reaction. To prepare nano-structured Cu loaded CeO2 catalysts, a combined method of the conventional impregnation and ammonium carbonate co-precipitation was examined. Morphology, crystal phase and surface structure of prepared catalysts were characterized using High-Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscopy (SEM) and Powder X-ray Diffraction (XRD). Catalytic properties of CuOx-CeO2 for CO oxidation were investigated in gas flow reactor system under atmospheric pressure and compared with copper oxide loaded zinc oxide. We expected that nano-structured CuOx-CeO2 catalysts could be used for removing CO produced in a wet reforming reaction of fuel cell applications.

Super-resolution technology has been applied to overcome the optical diffraction limit in recent years. In this work, optical super resolution based on Sb films has been studied. Experimental results show that the amorphous Sb–SR will considerably concentrate the energy into the center of the laser beam, while the crystal Sb–SR will not. Considering Sb as a semiconductor with a small energy gap, a three-order nonlinear response of surface plasmons is deduced to explain the phenomenon. Estimation is made and the calculated results are in agreement with the experimental results.

Pt-CeO(x)/C electrocatalysts for the improvement of oxygen reduction reaction (ORR) activity on cathode were prepared by a combined process of precipitation and co-impregnation methods. The Pt-CeO(x)/C electrocatalysts pretreated by the optimized electrochemical conditioning process showed high ORR activity as compared with homemade Pt/C electrocatalyst. Also, it showed high stability in the cyclic voltammetry (CV) test up to 1000 cycles into 0.5 M H(2)SO(4) aqueous solution. On the basis of the data of cyclic voltammogram of 30 cyclic sweeps, X-ray photoelectron spectroscopy, electron energy loss spectroscopy, high resolution transmission electron microscope image, and selected area electron diffraction analysis, it is concluded that the Pt-CeO(x) heterointerface involving the defect cluster formed by using optimized electrochemical pretreatment conditions on Pt in Pt-CeO(x)/C electro-catalyst contributes to the promotion of ORR activity and retention of its stability in long CV tests up to 1000 cycles.

Defect clusters with ordered structures in Gd-doped ceria have been verified by transmission electron microscopy. Atomistic simulation validates further the ordered structures and related pathway for cluster growth. A unique dumbbell structure formed with six oxygen vacancies in a ceria matrix has been identified as the building block for defect cluster growth and sequentially for the evolution from a F- to C-type lattice. As such, the phase transformation as established on the atomic scale occurs through this defect cluster growth.

To understand the ceria promotion effect of Pt-CeO(2)/C catalysts on methanol oxidation, microstructural and metal-oxide interactions of Pt-CeO(2)/C catalysts with an atomic ratio of Pt/Ce between 0.14 and 1.4 were systematically examined using high-resolution transmission electron microscopy and electron energy loss spectroscopy (EELS). With an increasing Pt content in the catalysts, Pt particles gradually invaded into the ceria supports and decoration on Pt particles was observed. Simultaneously, the morphology of the supports was dramatically modified with nanocrystalline and amorphous ceria formed between and/or around the Pt particles. It reveals that the Pt-ceria interaction could take place in the catalysts and the influence of the interaction was enhanced with an increasing Pt/Ce ratio. The EELS study demonstrated that the strong Pt-ceria interaction was related to the redox reaction between Pt and ceria. Experimental results also suggested that the strong interaction between Pt and ceria could contribute to the promotion effect of ceria on the oxidation of methanol.

Studies of electron energy loss spectroscopy and selected area electron diffraction (SAED) were systematically performed on 15 and 25 at. % lanthanide (Ln)-doped ceria samples (Ln=Sm, Gd, Dy, and Yb), through which the local ordering of oxygen vacancies that develops with increase in doping level was confirmed in the sequence of (Gd,Sm)>Dy>Yb. Furthermore, a monotone correlation between the development of the ordering and the degradation of ionic conductivity with increasing the doping concentration from 15 to 25 at. % was observed. Based on the analysis of SAED patterns, a structural model for the ordering of oxygen vacancies has been constructed, in which the arrangement of oxygen vacancies is similar to that in C-type Ln2O3 oxides and the 110 pairs of the vacancies are preferred. Then, the factors that can influence the formation of the ordering are discussed.

Ce1-xTb(x)O2-delta nano-powders have been successfully synthesized by using the ammonium carbonate coprecipitation method in an entire compositional range of 0or = xor = 1 by adjusting the preparation conditions. Studies of X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that the powders with different compositions mainly consist of fluorite structure. In addition, a small amount of secondary phase was observed in the powders with xor = 0.7. TEM observation indicated that the secondary phase could have a superstructure formed by a structural modulation of the fluorite structure.

The interaction between metal particles was calculated based on the discrete dipole method. The calculated results revealed that the multiple interactions in a collection of metal particles are dominated by the interaction between the neighboring particles. Thus, a two-particle approximation was deduced and applied to estimate the optical absorption and near-field enhancement property of Ag-Si3N4 composite films. The calculated results indicated that the interaction between Ag particles will induce extra absorption near the surface plasmon resonance peak and improve the near-field enhancement property of composite films. Calculated results were consistent with the experimental results.

Random Ag-SiN films consisting of random small Ag particles embedded in a SiN thin film were deposited by radiant-frequency magnetron sputtering. Specimens orderly comprising a random Ag-SiN film and an optical phase change recording layer were exposed to a focused laser beam. It showed that, with a random Ag-SiN layer deposited above the recording layer, the ablation of the recording layer occurred much faster and under much lower power than that of a single recording layer, which verified the local field enhancement of multiple scattering effects of the Ag particles. Finite Difference Time Domain (FDTD) calculation of a sandwiched structure consisting of ZnS-SiO 2 (130nm)/AgO x (20nm)/ZnS-SiO 2 (40nm) under a Gaussian beam irradiation has been carried out to simulate the near-field distribution in the structure. Near-field optical data storage adopting a Super-Resolution Near-field Structure (Super-RENS) usually utilizes similar films structure mentioned above to achieve super resolution storage density while getting a high Carrier to Noise Ratio (CNR) at the same time. Many recent works have reported that small Ag particles were formed in the AgOx film after converging laser irradiation onto the sandwiched structure. Here, another FDTD calculation was done to simulate the same model except for that small Ag particles were modeled in the AgO x film in the center region of the incident laser spot. The results showed a huge local near-field enhancement, which indicates that, if the structure full of such small Ag particles are formed in a tiny region beyond the optical diffraction limit, the optical recording and readout out density would be improved as well as a high CNR level achieved due to the multiple scattering of the Ag particles.

The optical properties of random Sb-SiN films in which Sb nano-particles are randomly dispersed were studied. Results show that the random Sb-SiN films possess high transmittance and low optical absorption. Additionally, some optical nonlinear phenomena of the random Sb-SiN films have been observed. Based on the special optical properties of random Sb-SiN films, they can be applied in many fields, for example, optical storage and optical microscopy. When the random Sb-SiN film was prepared close to a phase-change-recording layer, it decreases the threshold of input power for recording and speeds up the phase transition of recording media, and also improves the resolving power of readout system. On the other hand, while the random Sb-SiN films were deposited on the slide glass used in far-field optical microscopy, it obviously improves the resolving power of optical microscope and reduces the value of resolution limit to less than half of the value calculated by the expression given by Lord Rayleigh.

Mechanism of Sb-SR (Sb-type super-resoluiton near-field structure) was studied. Experimental results show that the super-resolution performance of amorphous Sb-SR is considerably better than crystal Sb-SR. Considering that Sb is a semi-conductor with small energy gap, a three-order nonlinear response of surface plasmons is deduced to explain the performance of amorphous Sb-SR. Estimation is made and the calculated results are in agreement with the experimental results. Under the new approach, other semiconductors with small energy gap may possibly possess super-resolution performance.

Nonlinear optical transimittance in the Super-RENS (super-resolution near-field structure) [glass/SiN(2Onm)/ Sb(lSnm)/SiN(2Onm)] was investigated using a static transmittance measuring system with a focused laser illumination. Theresult shows an optical switching property with a strong nonlinear effect. Some SEM(Sanning Electron Microscope)images ofrecording spots in a PC(Phase Change) GeSbTe layer with and without the Super-RENS layers covering on itare presented. The images demonstrate the field enhancement effect due to the Super-RENS layers. The cause of theenhancement is considered as the local plasmon excitation.Keywords : super-resoluti on near-field structure (S uper-REN 5), near-fl eld optical recording, local plasmon

Under the influence of a direct current (dc), phase transformation could take place at the interface between platinum anode and holmium-doped ceria (HDC) electrolyte at temperature ≥600 °C. This transformation is insensitive to the doping concentration and the sintering temperature, but strongly depends on the testing temperature. As a result of the dc-induced transformation, products with a size up to hundreds of microns were separated from the anode-side surface and, correspondingly, circular holes with diameters varied from tens to hundreds of microns remained on the surface. Compared with original HDC samples, a high degree of local ordering of oxygen vacancies was found in most of the products. Based on structural and compositional studies, it is suggested that the dc-induced transformation could be attributed to the electrochemical reaction at the anode/electrolyte interface and the mobility of Ho cations promoted by the current.

As a promising electrolyte material for intermediate-temperature solid oxide fuel cells operated at a temperature of

Intragranular distributions of composition and valent state in sintered Tb-doped ceria have been systematically investigated. Through detailed studies of electron energy loss spectroscopy and energy filtering transmission electron microscopy, both compositional and valent state inhomogeneities of Ce and Tb were confirmed, which are related to the existence of nanosized domains in Tb-doped ceria. Compared with their matrix, the domains have higher Tb concentration and Ce and Tb cations in the domains tend to be trivalent. Furthermore, ordering of oxygen vacancies in the domains, which increases with increasing doping concentration, has been determined by EELS.

Inhomogeneous microstructures, including nanosized domains and nanoprecipitates, were observed in sintered samples of holmium-doped ceria. The formation of such microstructural inhomogeneity is related to the segregation of dopant cations and can be enhanced by increasing doping concentration and sintering temperature. Through examination of the relationship between the microstructures and electrical properties, it was found that the inhomogeneity can have negative impacts on ionic conduction, which could be explained in terms of the interaction between the oxygen vacancies and the segregated dopant cations. (C) 2007 The Electrochemical Society.

The ionic conductivities and microstructures of Ce1-xYbxO2-x/2 ( x = 0.10, 0.15, 0.20, and 0.25 ) with average grain sizes in a range of 0.2 - 3.7 mu m were studied systematically. Nanosized domains were confirmed through detailed studies of transmission electron microscopy. The relationships of the domains, doping concentration, and grain size were determined, and their effects on the ionic conductivities were examined. It was concluded that the domains were formed via the segregation of Yb cations so that they could trap the oxygen vacancies and lower the conductivity. Furthermore, the development of the domains, which depends on the doping concentration and grain size, can affect the doping concentration and grain-size dependencies of the conductivity. (c) 2006 The Electrochemical Society.