Ceria Samples Research Articles

Beam heating from a fourth-generation synchrotron source.

The high levels of flux available at a fourth-generation synchrotron are shown to have significant beam heating effects for high-energy X-rays and radiation hard samples, leading to temperature increases of over 400 K with a monochromatic beam. These effects have been investigated at the ID11 beamline at the recently upgraded ESRF Extremely Brilliant Source, using thermal lattice expansion to perform in situ measurements of beam heating. Results showed significant increases in temperature for metal and ceria samples, which are compared with a lumped thermodynamic model, providing a tool for estimating beam heating effects. These temperature increases may have a drastic effect on samples and measurements, such as the rapid recrystallization of a copper wire shown here. These results demonstrate the importance of beam heating and provide information needed to consider, predict and mitigate these effects.

Elucidating the Mechanism of Ambient-Temperature Aldol Condensation of Acetaldehyde on Ceria.

Using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations, we conclusively demonstrate that acetaldehyde (AcH) undergoes aldol condensation when flown over ceria octahedral nanoparticles, and the reaction is desorption-limited at ambient temperature. trans-Crotonaldehyde (CrH) is the predominant product whose coverage builds up on the catalyst with time on stream. The proposed mechanism on CeO2(111) proceeds via AcH enolization (i.e., α C–H bond scission), C–C coupling, and further enolization and dehydroxylation of the aldol adduct, 3-hydroxybutanal, to yield trans-CrH. The mechanism with its DFT-calculated parameters is consistent with reactivity at ambient temperature and with the kinetic behavior of the aldol condensation of AcH reported on other oxides. The slightly less stable cis-CrH can be produced by the same mechanism depending on how the enolate and AcH are positioned with respect to each other in C–C coupling. All vibrational modes in DRIFTS are identified with AcH or trans-CrH, except for a feature at 1620 cm–1 that is more intense relative to the other bands on the partially reduced ceria sample than on the oxidized sample. It is identified to be the C=C stretch mode of CH3CHOHCHCHO adsorbed on an oxygen vacancy. It constitutes a deep energy minimum, rendering oxygen vacancies an inactive site for CrH formation under given conditions.

Synthesis of nickel oxide/gadulinium doped ceria nanostructures by new methods as anode material for solid oxide fuel cells: Ni(II) complexes as new precursors

Nickel oxide /gadolinium dopped ceria nano powders, NiO/GDC, (NGC) with controlled morphology were synthesized by the sol-gel method. The nickel(II) coordination compounds have been used as new precursors for the preparation of ceramic material, NiO/GDC, as anodic powders for application in solid oxide fuel cell. The formation of diverse morphologies with different porosity was observed by varying the Nickel(II) coordination compounds, [NiL2(µ-acetylenedicarboxylate)]n, [NiL2(µ-terephthalate)]n and [NiL2(µ-2,6 pyridinedicarboxylate)]n,. Then three different kinds of nickel oxide / gadolinium dopped ceria, NGC (a), NGC (b), and NGC (c) samples of different shapes were developed by new precursors. Thiese powders have been used as electrocatalyst for solid oxide fuel cell. The catalytic performance of NGC anodes for the hydrogen oxidation reaction was analyzed via impedance spectra test using yttria-stabilized zirconia (YSZ)-supported symmetry half-cell. The modified NGC (c) anode powder fabricated with the new precursor of [NiL2(µ-2,6 pyridinedicarboxylate)]n (N’-(pyridine-3-yl)methylene)isonicotinohydrazide (L)) presented the least polarization resistivity of 0.106 Ω. cm2 measured at 800 ℃ under humidified H2. The NGC (c) anode powder with a better pore distribution and excellent microstructure demonstrated the most desirable electro-catalytic activity.

Facile synthesis of ceria-based composite oxide materials by combustion for high-performance solid oxide fuel cells

This article proposes the preparation of promising oxide materials with a broad range of applications as electrolytic materials for solid oxide fuel cells (SOFCs). The oxide materials, namely, samarium-doped ceria Sm0.2Ce0.8O (SDC), gadolinium-doped ceria Gd0.2Ce0.8O (GDC), and calcium-doped ceria Ca0.2Ce0.8O (CDC), were prepared through the conventional combustion method with glycerol as a complexing agent. The thermal behavior of the materials was examined through thermogravimetry-differential scanning calorimetry measurements, and their structural and morphological properties were analyzed via X-ray diffractometry (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Fourier transform infrared spectroscopy confirmed the presence of the metal oxide group in the range of 400–1500 cm−1. Two probe methods were used for electrical measurements. The XRD patterns obtained confirmed that the materials have cubic fluorite structures with an average crystallite size in the range of 26.8–44.7 nm. The ionic conductivities of the ceria samples were measured in the temperature between 300 and 700 °C. The samples consistently showed semiconducting behavior, with SDC exhibiting the highest ionic conductivity of 8.32 × 10−3 S/cm. A maximum power density of 265 mW/cm2 was recorded at 650 °C when SDC was used as an electrolyte.

Gas Phase Glycerol Valorization over Ceria Nanostructures with Well-Defined Morphologies.

Glycerol solutions were vaporized and reacted over ceria catalysts with different morphologies to investigate the relationship of product distribution to the surface facets exposed, particularly, the yield of bio-renewable methanol. Ceria was prepared with cubic, rodlike, and polyhedral morphologies via hydrothermal synthesis by altering the concentration of the precipitating agent or synthesis temperature. Glycerol conversion was found to be low over the ceria with a cubic morphology, and this was ascribed to both a low surface area and relatively high acidity. Density functional theory calculations also showed that the (100) surface is likely to be hydroxylated under reaction conditions which could limit the availability of basic sites. Methanol space-time-yields over the polyhedral ceria samples were more than four times that for the cubic material at 400 °C, where 201 g of methanol was produced per hour per kilogram of the catalyst. Under comparable glycerol conversions, we show that the rodlike and polyhedral catalysts produce a major intermediate to methanol, hydroxyacetone (HA), with a selectivity of ca. 45%, but that over the cubic sample, this was found to be 15%. This equates to a 13-fold increase in the space-time-yield of HA over the polyhedral samples compared to the cubes at 320 °C. The implications of this difference are discussed with respect to the reaction mechanism, suggesting that a different mechanism dominates over the cubic catalysts to that for rodlike and polyhedral catalysts. The strong association between exposed surface facets of ceria to high methanol yields is an important consideration for future catalyst design in this area.

Heat capacities and thermodynamic functions of neodymia and samaria doped ceria

Doped ceria materials are ionic conductors currently under investigation for use in solid oxide fuel cells, catalysts, and other applications. We measured the heat capacity of several doped ceria samples from 1.8 K to 300 K to better understand their physical properties. The samples used in this study were either singly doped with Nd or Sm, or co-doped with both Nd and Sm. This work complements an earlier detailed study of their heats of formation and ionic conductivity. Here we provide the thermodynamic functions based on theoretical fits of our heat capacity measurements including Cp,m°, Δ0TSm°, Δ0THm°, and Φm°. We also detected splitting of nuclear magnetic states, which appeared as an upturn in the heat capacity below 10 K. We observed this phenomenon in all samples and provide calculations of the local magnetic field causing the splitting.

Self-assembly of structured CeCO3OH and its decomposition in H2 for a novel tactic to obtain CeO2- with excellent photocatalytic property

Abstract In this work, various new-observed structured CeCO3OH were synthesized by a self-assembly hydrothermal method, and a novel tactic to produce CeO2-x with excellent photocatalytic activity by decomposing CeCO3OH in H2 was proposed and identified. By controlling the synthetic conditions, almond-like, subglobose shape and hollow-sphere of CeCO3OH, 3D-broom-like of Ce2O3·2CO2·nH2O (n = (1–2)), and sheet-like of Ce2(CO3)3·6H2O were synthesized. The crystal growth and formation of the cerium carbonate compounds were carefully studied using XRD, SEM and TEM. TG, thermodynamic calculation and in-situ XRD were employed to reveal the decomposition behavior of almond-like CeCO3OH in air, Ar and H2. The results show that the decomposition temperatures of CeCO3OH in Ar and H2 are higher than that of in air, and suggest that Ce2O3 has a low thermodynamic stability during the decomposition of CeCO3OH in Ar and H2, and Ce3+ will be mostly oxidized by H2O firstly and then by both of H2O and CO2. The ceria samples obtained by decomposing from CeCO3OH in different atmosphere maintain indistinguishable shape and particle size. The XPS, Raman spectra and ESR results indicate that the one obtained in H2 has the richest surface oxygen vacancies (OVs), narrowest band gap of 3.12 eV, lowest intensity in PL spectra and a significantly enhanced photodegradation ratio of methylene blue. The MB photodegradation ratio after 120 min reaction with the catalysts of CeO2-Air, CeO2-Ar and CeO2-H2 is 43.14%, 54.43% and 73.41%, with a calculated reaction rate constant of 0.00539, 0.00652 and 0.01097 min-1, respectively. The offered novel tactic of decomposing CeCO3OH in H2 is an efficient and facile technique for active CeO2-x production.

Characterizations and photocatalytic activity of ceria nanoparticles synthesized in KCl–LiCl/KOH–NaOH molten flux from different precursors

Molten salts synthesis (MSS) is a simple and potential technique for ceria nanoparticles (NPs) production, but the relevant effects of salt medium and cerium precursor on the synthesized ceria NPs need further attention. In the present work, we investigated the influences of frequently employed KCl–LiCl and KOH–NaOH molten flux and typical inorganic cerium precursors on the characterizations and photocatalytic property of ceria NPs. Results show that the CeO2 NPs obtained in molten KOH–NaOH flux have smaller particle/crystal sizes but more serious agglomeration than that from KCl–LiCl flux. UV–Vis DRS spectra reveal that the ceria synthesized in molten hydroxides from the cerium nitrate precursor has the narrowest band gap of 2.87 eV in studied ceria samples. The ceria NPs obtained from KCl–LiCl flux have wider band gaps of 3.15–3.29 eV and faster recombination rates of photo-generated e− and h+. It was found that the ceria NPs obtained in molten KCl–LiCl salt show better photocatalytic activities for methylene blue (MB) degradation and may be due to the uniform size distribution and well-dispersed particles.

A novel ceria hollow nanosphere catalyst for low temperature NOx storage

In this work, a highly active CeO2 catalyst with hollow nanosphere morphology for low temperature NOx storage was prepared by a surfactant-assisted solvothermal reaction. The physicochemical properties of ceria samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption–desorption, H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS). The as-prepared CeO2 nanosphere possesses excellent NO oxidation capacity, smaller mesopores, better reducibility and more surface Ce3+ content. Compared with CeO2 with nanorod and nanoparticle morphologies, CeO2 nanosphere shows better intrinsic low temperature NOx trapping performance, with a wide operating temperature window (150–300 °C), high NOx adsorption capacity (NAC, 640–745 μmol/g) and high NOx storage capacity (NSC, 250–350 μmol/g). Two reaction pathways are speculated for NOx adsorption on CeO2 nanosphere, including “nitrate route” and “nitrite route”. The thermally unstable surface nitrites formed on the CeO2 nanosphere allow ceria to release more NOx during the desorption process. The present work provides a new ceria morphology for NOx traps, which may become a potential excellent NOx storage material.

Enhancement of electrical properties Ce0.8Sm0.2−xO2−δ by Sr2+ doping

Nanocrystalline strontium co-doped Samarium Doped Ceria samples with different compositions Ce0.8Sm0.2−xSrxO2−δ (x = 0.05, 0.1, 0.15, 0.2) prepared by the citrate gel method. X-ray diffraction tools confirm the structure of the system. Field Emission Scanning Electron Microscopy images detail the microstructure of the sintered pellets grain and grain boundaries. The elemental content of the compositions confirmed by Energy Dispersive Spectroscopy analysis. The presence of concentrated O2- vacancies in the strontium co-doped Samarium Doped Ceria samples analyzed from the Raman Spectroscopy. Electrical properties of the sintered pellets are analyzed in terms of ac data from ac complex impedance spectroscopy. Normalization of modulus spectra of the prepared samples shows the low value of stretching factor (β) less than 1, which indicates a non-Debye relaxation process. The Arrhenius plots for all compositions show as the temperature increases; there is an increase in the value of conductivity, which indicates that the prepared samples follow a negative temperature coefficient of resistance. The combined analysis of impedance, modulus, and electrical conductivity attains value suitable for solid oxide fuel cell applications. Among the different compositions, Ce0.8Sm0.05Sr0.15O2−δ samples exhibit a maximum conductivity of 3.39 × 10−4 Scm−1 at 750 °C.

Europium-Doped Ceria-Gadolinium Mixed Oxides: PARAFAC Analysis and High-Resolution Emission Spectroscopy under Cryogenic Conditions for Structural Analysis.

Gadolinium-doped ceria or gadolinium-stabilized ceria (GDC) is an important technical material due to its ability to conduct O2- ions, e.g., used in solid oxide fuel cells operated at intermediate temperature as an electrolyte, diffusion barrier, and electrode component. We have synthesized Ce1-xGdxO2-y:Eu3+ (0 ≤ x ≤ 0.4) nanoparticles (11-15 nm) using a scalable spray pyrolysis method, which allows the continuous large-scale technical production of such materials. Introducing Eu3+ ions in small amounts into ceria and GDC as spectroscopic probes can provide detailed information about the atomic structure and local environments and allows us to monitor small structural changes. This study presents a novel approach to structurally elucidate europium-doped Ce1-xGdxO2-y:Eu3+ nanoparticles by way of Eu3+ spectroscopy, processing the spectroscopic data with the multiway decomposition method parallel factor (PARAFAC) analysis. In order to perform the deconvolution of spectra, data sets of excitation wavelength, emission wavelength, and time are required. Room temperature, time-resolved emission spectra recorded at λex = 464 nm show that Gd3+ doping results in significantly altered emission spectra compared to pure ceria. The PARAFAC analysis for the pure ceria samples reveals a high-symmetry species (which can also be probed directly via the CeO2 charge transfer band) and a low-symmetry species. The GDC samples yield two low-symmetry spectra in the same experiment. High-resolution emission spectra recorded under cryogenic conditions after probing the 5D0-7F0 transition at λex = 575-583 nm revealed additional variation in the low-symmetry Eu3+ sites in pure ceria and GDC. The total luminescence spectra of CeO2-y:Eu3+ showed Eu3+ ions located in at least three slightly different coordination environments with the same fundamental symmetry, whereas the overall hypsochromic shift and increased broadening of the 5D0-7F0 excitation in the GDC samples, as well as the broadened spectra after deconvolution point to less homogeneous environments. The data of the Gd3+-containing samples indicates that the average charge density around the Eu3+ ions in the lattice is decreased with increasing Gd3+ and oxygen vacancy concentration. For reference, the Judd-Ofelt parameters of all spectra were calculated. PARAFAC proves to be a powerful tool to analyze lanthanide spectra in crystalline solid materials, which are characterized by numerous Stark transitions and where measurements usually yield a superposition of different contributions to any given spectrum.

Manganese-doped, hydrothermally-derived ceria: The occurrence of birnessite and the distribution of manganese

Ceria doped with manganese in various amounts was prepared via hydrothermal synthesis. XRD revealed that beside ceria, monoclinic birnessite (Na0.55Mn2O4 × 1.5H2O) appears in the samples. The occurrence of birnessite was achieved using different synthesis conditions and precursors. SEM imaging revealed birnessite layered formations surrounded with ceria nanoparticles, while EDS confirmed the presence of both phases. Weight percentage, lattice constants and crystallite size of ceria, as well as birnessite, were obtained through whole powder pattern decomposition. Pure and Mn doped ceria samples with crystallite sizes between 3.1 and 3.4 nm, and specific surface area values between 183 and 212 m2 g−1 were obtained. It was established that the amount of Mn entering the ceria lattice or forming birnessite varies with nominal composition. Introduction of Mn in ceria is evident from the decrease of ceria lattice constant (from 5.4185 Å to 5.4002 Å). The entrance of manganese in the ceria crystal lattice was confirmed via EDS spectroscopy. Thermally induced changes were monitored via DTA/TGA, XRD and FTIR. Birnessite decomposes below 200 °C, while thermal treatment at 500 °C for 2 h yields Na2Mn5O10. Weight percentage of birnessite was confirmed through calculations based on the loss of interlayer water during TGA analysis. HRTEM revealed nanorod morphology of Na2Mn5O10, while EELS gave insight into the composition of this phase.

An algorithm for correcting systematic energy deficits in the atom probe mass spectra of insulating samples

Improvements in the mass resolution of a mass spectrometer directly correlate to improvements in peak identification and quantification. Here, we describe a post-processing technique developed to increase the quality of mass spectra of strongly insulating samples in laser-pulsed atom probe microscopy. The technique leverages the self-similarity of atom probe mass spectra collected at different times during an experimental run to correct for electrostatic artifacts that present as systematic energy deficits. We demonstrate the method on fused silica (SiO2) and neodymium-doped ceria (CeO2) samples which highlight the improvements that can be made to the mass spectrum of strongly insulating samples.

Pelletized Cu-Ni/CePr5 catalysts for H2 purification via Water Gas Shift reaction

Water Gas Shift (WGS) reaction recently gained attraction as a purifying method to remove CO in H2 stream produced from bio-alcohols reforming for fuel cells applications. In previous works, we tested Cu-Ni samples supported on Pr promoted ceria as catalysts for WGS reaction. However, powder samples are not recommended for a scale-up process and ceria samples lack of cohesive forces to obtain a pellet. Then, supported catalysts can be an interesting alternative to study. In the present work, alumina spheres were impregnated in order to replicate the same chemical formulation of powder-state samples. It was studied the influence in catalytic performance of several textural and catalytic features such as: pellet size, active phase content and distribution, Cu:Ni ratio in bimetallic samples, and contact time. The Cu samples showed a moderate activity and the Ni ones a better performance, but tendency to generate CH4. For all catalysts, the decrease in the pellet size induced a higher CO conversion, indicating strong mass diffusion effects. Besides, it was observed that small addition of Cu to Ni samples significantly moderated the methanation reaction, but maintaining the activity. The change in active metal content slightly modified the activity and changed the selectivity, in agreement with the characterization techniques results (H2-TPR and OSC). In summary, the sample with Cu:Ni ratio equal to 1:2 with 1.5 wt%, presented a great performance, by removing 8 to 2 %v/v of CO with an acceptable contact time and high selectivity, being the most promissory catalyst for higher scale tests.

The activation and conversion of carbon dioxide on the surface of zirconia-promoted ceria oxides

This study reports the conversion of carbon dioxide (CO2) by ceria (CeO2)-zirconia (ZrO2) composites with various ZrO2 contents (0, 20, 50, 80 and 100 %). The modification introduced by ZrO2 altered the structural properties of the ceria samples, affecting their reducibility and subsequent activity to convert CO2. The characterisation results showed a clear relationship between the structural properties of the materials and the activity for CO2 conversion. The addition of ZrO2 was effective to improve a close interaction between CeO2 and ZrO2 and induced the formation of structural defects that further promoted oxygen transport and facilitated the creation of oxygen vacancies that were critical for CO2 conversion. All samples investigated were found to be effective in converting CO2 into carbon monoxide (CO) at 450 °C, and the addition of ZrO2 was also found to be effective in improving the thermal resistance and stabilising the crystalline structure of the samples especially when the ZrO2 content was > 50 %. When the content of ZrO2 controlled between 50 % and 80 %, the onset temperature for CO2 conversion was found to be 285 °C, which was about 80 °C lower than that required for the sample without ZrO2 modification. Thus, modifying CeO2 by ZrO2 was effective to prevent both the textural and structural alteration of the samples under a high temperature environment as well as cyclic redox operations, resulting in a constant and high degree of CO2 conversion into CO.

Synthesis, Characterisation and the photocatalytic performance of europium oxide/ceria nanocomposite

ABSTRACT Different loadings of europium were doped into commercial ceria nanoparticles by using europium nitrate solution followed by thermal treatment. The characterisation results showed a formation of Eu2O3 nanoparticles covering the ceria particles; moreover, the density of such cover is increased with europium loading. The photocatalytic performance of the prepared samples was evaluated in the photocatalytic decolourization reaction of methyl green under the illumination of UV black light with an average wavelength of 367 nm. The reaction rate of europium-doped ceria was 4.5–10 times higher compared to the neat ceria sample.

Investigation of Zr, Gd/Zr, and Pr/Zr – doped ceria for the redox splitting of water

There is a renewed interest in CeO2 for use in solar-driven, two-step thermochemical cycles for water splitting. However, despite fast reduction/oxidation kinetics and high thermal stability of ceria, the cycle capacity of CeO2 is low due to thermodynamic limitations. In an effort to increase cycle capacity and reduce thermal reduction temperature, we have studied binary zirconium-substituted ceria (ZrxCe1-xO2, x = 0.1, 0.15, 0.25) and ternary praseodymium/gadolinium-doped Zr-ceria (M0.1Zr0.25Ce0.65O2, M = Pr, Gd). We evaluate the oxygen cycle capacity and water splitting performance of crystallographically and morphologically stable powders that are thermally reduced by laser irradiation in a stagnation flow reactor. The addition of zirconium dopant into the ceria lattice improves O2 cycle capacity and H2 production by approximately 30% and 11%, respectively. This improvement is independent of the Zr dopant level, up to 25%, suggesting that above 10% Zr dopant level, Zr might be displaced during the high temperature annealing process. The addition of Pr and Gd to the binary Zr-ceria mixed oxide, on the other hand, is detrimental to H2 production. A kinetic analysis is performed using a model-based analytical approach to account for effects of mixing and dispersion, and to identify the rate controlling mechanism of the water splitting process. We find that the water splitting reaction at 1000 °C and with 30 vol% H2O, for all doped ceria samples, is surface limited and best described by a deceleratory power law model (F-model), similar to undoped CeO2. Additionally, we used density functional theory (DFT) calculations to examine the role of Zr, Pr, and Gd. We find that the addition of Pr and Gd induce non-redox active sites and, therefore, are detrimental to H2 production, in agreement with experimental work. The calculated surface H2 formation step was found to be rate limiting, having activation barriers greater than bulk O diffusion, for all materials. This agrees with and further explains experimental findings.

Transport Properties and High Temperature Raman Features of Heavily Gd-Doped Ceria

Transport and structural properties of heavily doped ceria can reveal subtle details of the interplay between conductivity and defects aggregation in this material, widely studied as solid electrolyte in solid oxide fuel cells. The ionic conductivity of heavily Gd-doped ceria samples (Ce1−xGdxO2−x/2 with x ranging between 0.31 and 0.49) was investigated by impedance spectroscopy in the 600–1000 K temperature range. A slope change was found in the Arrhenius plot at ~723 K for samples with x = 0.31 and 0.34, namely close to the compositional boundary of the CeO2-based solid solution. The described discontinuity, giving rise to two different activation energies, points at the existence of a threshold temperature, below which oxygen vacancies are blocked, and above which they become free to move through the lattice. This conclusion is well supported by Raman spectroscopy, due to the discontinuity revealed in the Raman shift trend versus temperature of the signal related to defects aggregates which hinder the vacancies movement. This evidence, observable in samples with x = 0.31 and 0.34 above ~750 K, accounts for a weakening of Gd–O bonds within blocking microdomains, which is compatible with the existence of a lower activation energy above the threshold temperature.

Enhancement of catalytic activity by UV-light irradiation in CeO2 nanocrystals

Ultraviolet (UV) light irradiation on CeO2 nanocrystals catalysts has been observed to largely increase the material’s catalytic activity and reactive surface area. As revealed by x-ray absorption near edge structure (XANES) analysis, the concentration of subvalent Ce3+ ions in the irradiated ceria samples progressively increases with the UV-light exposure time. The increase of Ce3+ concentration as a result of UV irradiation was also confirmed by the UV-vis diffuse reflectance and photoluminescence spectra that indicate substantially increased concentration of oxygen vacancy defects in irradiated samples. First-principle formation-energy calculation for oxygen vacancy defects revealed a valence-hole-dominated mechanism for the irradiation-induced reduction of CeO2 consistent with the experimental results. Based on a Mars-van Krevelen mechanism for ceria catalyzed oxidation processes, as the Ce3+ concentration is increased by UV-light irradiation, an increased number of reactive oxygen atoms will be captured from gas-phase O2 by the surface Ce3+ ions, and therefore leads to the observed catalytic activity enhancement. The unique annealing-free defect engineering method using UV-light irradiation provides an ultraconvenient approach for activity improvement in nanocrystal ceria for a wide variety of catalytic applications.

Preparation and properties of ceramic electrolytes in the Nd and Gd Co-doped ceria systems prepared by polyol method

In this research, a straightforward polyol method has been successfully applied to synthesize Nd0.20GdxCe0.8−xO1.9−x/2 (x = 0, 0.05, 0.10, 0.15, 0.20), (NGDC) rare-earth-co-doped ceria electrolytes. Instead of the nitrate compounds generally used as starting materials, acetate compounds of cerium and dopants, triethylene glycol as solvent and reducing agent were used. A single fluorite phase was obtained after a low temperature (600 °C) calcination treatment. A series of NGDC electrolytes are fabricated at the sintering temperature of 1400 °C for 6 h. Most of them have relative densities more than 93%. According to the results of X-ray diffraction of neodymium and gadolinium doped electrolytes, all NGDC electrolytes can be produced in a single phase without any other impurity phase. Relative density of NGDC electrolytes increased first and then decreased with the increase of the Gd3+ additive ratio. The total ionic conductivity of the doped and co-doped ceria samples were studied in the temperature range 500–800 °C by using the two-probe AC impedance spectroscopy. It was found that the incorporation of a small amount of cation Gd3+ into the solid solution Nd0.20GdxCe0.8−xO1.9−x/2 allowed an increase in the ionic conductivity of the Nd0.20Ce0.80O1.90 oxide electrolyte.