Samarium Doped Cerium Oxide Research Articles

Samarium doped cerium oxide nanoparticles under extreme temperatures and its photocatalysis activity on tetracycline

In this work, we report the characterization and application of cerium oxide (CeO2) doped with samarium (Sm). The physical and chemical properties of these Sm-CeO2 are discussed in comparison with their pure cerium oxide counterparts. Raman spectroscopy measurements under extreme temperature conditions showed that the vibrational optical modes at 267 cm−1, 458 cm−1, 555 cm−1 and 603 cm−1, except for the mode 555 cm−1, exhibited a red shift with increasing temperature with different temperature coefficients θ = ∂ω/∂T. The first-order temperature coefficient θ of the mode 458 cm−1 is ∼ (−0.01154 ± 4.4 × 10−4 cm−1/K). In contrast, the second-order mode coefficient at ∼267 cm−1 which equal ∼ (−0.04949 ± 2 × 10−3 cm−1/K) is higher, as well as that of modes 555 cm−1 and 603 cm−1 which are equivalent to ∼ (−0.01339 ± 2.6 × 10−3 cm−1/K) and (−0.00575 ± 1.89 × 10−3 cm−1/K). If based on the evolution of the analyzed Raman spectra that no structural phase transition of the crystal was observed for high and low temperatures, only a conformational change at temperatures of 553 and 733 K, which may be associated with the formation of oxygen vacancies in the lattice of Sm-CeO2. We also show the efficiency of the Sm-CeO2 sample for applications in Photocatalysis demonstrated through the removal of the Tetracycline (TC) drug in comparison with the pure CeO2 sample. The photocatalytic experiments showed a significant increase in TC removal efficiency in a remarkable synergistic effect between adsorption and photocatalysis, leading to approximately 83 % TC removal for Sm-CeO2.

Samarium doped cerium oxide thin films deposited by pulsed laser deposition

Samarium doped ceria thin films are an important material for the electrochemical devices. Fluorite structured Samarium Doped Cerium Oxide (SDC) thin films were deposited on Si (100) at 500 °C and 600 °C substrate temperatures by PLD (Pulsed Laser Deposition) from Sm0,24 Ce0,13 O0.63 target. X-ray Diffraction (XRD) proved the existence of SDC crystalline compound in both samples, deposited at 500 and 600 °C but not in the target. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) investigations revealed a high quality of the films, with lower roughness, of under 5 nm in the case of the sample deposited at 600 °C. The beginning of sintering process was evidenced by SEM in the case of samples deposited at 600 °C. X-ray Photoelectron Spectroscopy (XPS) indicated the increasing proportion of Ce3+ for PLD films comparatively to the target, in both cases, of substrate temperatures of 500 and of 600 °C, higher in the first case. Spectroscopic Ellipsometry (SE) investigation permitted the calculation of a refractive index under 2.2 in the visible (Vis)-near infrared (near-IR) domain for both samples. Nanoindentation tribometric measurements concluded that both elasticity modulus and hardness decreases with substrate temperature increasing. The obtained films are candidates for potential uses as electrolyte material for a new generation of electrochemical devices.

Structural regulation and polishing performance of dendritic mesoporous silica (D-mSiO2) supported with samarium-doped cerium oxide composites

Ceria (CeO2) particles are prevalent polishing abrasive materials. Trivalent lanthanide ions are the popular category of dopants for enriched surface defects and thus improved physicochemical properties, since they are highly compatible with CeO2 lattices. Herein, a series of dendritic-like mesoporous silica (D-mSiO2)-supported samarium (Sm)-doped CeO2 nanocrystals were synthesized via a facile chemical precipitation method. The relation of the structural characteristics and chemical mechanical polishing (CMP) performances were investigated to explore the effect of Sm-doping amounts on the D-mSiO2/SmxCe1−xO2−δ (x = 0–1) composite abrasives. The involved low-modulus D-mSiO2 cores aimed to eliminate surface scratch and damage, resulting from the optimized contact behavior between abrasives and surfaces. The trivalent cerium (Ce3+) and oxygen vacancy (VO) at CeO2 surfaces were expected to be reactive sites for the material removal process over SiO2 films. The optimal oxide-CMP performances in terms of removal efficiency and surface quality were achieved by the 40% Sm-doped composite abrasives. It might be attributed to the high Ce3+ and VO concentrations and the enhancement of tribochemical reactivity between CeO2SiO2 interfaces. Furthermore, the relationship between the surface chemistry, polishing performance as well as the actual role in oxide-CMP of the D-mSiO2/SmxCe1−xO2−δ abrasives were also discussed.

Synthesis of samarium-doped cerium oxide nanoparticles with room-temperature ferromagnetism by modified hydrothermal method

Synthesis of samarium-doped cerium oxide nanoparticles with room-temperature ferromagnetism by modified hydrothermal method

Tailoring the activation energy and the ionic properties of bismuth codoped SDC powder prepared by solid-state reaction method

Research on fuel cell components has received great attention owing to the growing need for sustainable energy sources. Bismuth (Bi3+) codoped samarium-doped cerium oxide [Ce1−xSmx−yBiyO2−δ (x = 0.2 and y = 0, 0.05 and 0.1)] nanosystems were prepared by solid-state reaction method. Rietveld structure refinement of X-ray diffraction pattern confirms the cubic fluorite structure along the (111) plane with the decrease in lattice distortion. At the same sintering temperature, pellets exhibit good morphology with better mechanical strength. The conductivity measurements carried out using the Nyquist plot, as well as the modulus spectra, indicate the effect of grain and grain boundary conduction at high temperatures. With the increase in the incorporation of Bi dopant, there is a gradual decrease in ionic conductivity and activation energy. The composition of Ce0.8Sm0.1Bi0.1O2−δ exhibits less ionic conductivity compared to other samples due to the oxygen vacancies attracted by dopant cations. The effect of Bi3+ dopants on samarium-doped ceria lattice structures and the electrical properties of the systems have been discussed.

Effect of iron oxide co-doping on structural, thermal, and electrochemical properties of samarium doped ceria solid electrolyte

Samarium doped cerium oxide (SDC) is widely investigated as an electrolyte material for solid oxide fuel cells (SOFCs) applications. However, the pristine SDC suffers from limited conductivity and stability. In this work, we prepare iron oxide (FeO) co-doped SDC electrolyte material via the solid-state method for SOFCs applications. The microstructural, thermal, and ionic conductivities of FeO/SDC electrolyte are investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), thermogravimetric analysis (TGA), and electrochemical impedance spectroscopy (EIS) respectively. The XRD and SEM studies confirm that as-prepared electrolyte is single phase and dense homogenous structure respectively. The EIS analysis exhibits the highest ionic conductivity of ~0.147 S/cm at 600 °C along with power density ~552 mW/cm2 and open-circuit voltage (OCV) 1.3 V in the solid oxide electrolysis cell.

Electronic structure and photocatalytic activity of samarium doped cerium oxide nanoparticles for hazardous rose bengal dye degradation

Sm doped CeO2 (Sm = 0%, 2%, 4%, 6% and 8%) nanoparticles have been synthesized by sol-gel method for spintronics and photodegradation applications. Structural properties were studied using X-ray diffraction that showed single-phase crystalline nature with some structural distortions. Raman spectroscopy was employed to study the defects where longitudinal optical mode confirmed the presence of defects in the form of oxygen vacancies. Magnetic studies infer that saturation magnetization (MS) increased with Sm doping from 0.36 × 10−3 emu/g for pure CeO2 to 15.8 × 10−3 emu/g for Sm 6% and then, decreased for Sm 8%. Reported results also demonstrated the excellent photodegradation of UV-irradiated rose bengal dye. X-ray photoelectron spectroscopy (XPS) was used to illustrate the electronic structure, including the contribution of each ionic state, i.e. Ce3+ and Ce4+. Oxygen vacancies and formation of new networks led to the origin of room temperature ferromagnetic behaviour and excellent photocatalytic degradation of harmful rose bengal dye.

Effects of TiO2 and SDC addition on the properties of YSZ electrolyte

In this study, we investigate the effects of adding titanium dioxide (TiO2) and samarium doped cerium oxide (SDC) on the properties of yttrium-stabilized zirconia (YSZ) electrolyte. The microstructure, mechanical, and electrochemical properties of the electrolyte are investigated. The performance in CO2 electrolysis is measured by supplying carbon dioxide to Ni-YSZ electrode and nitrogen to LSM electrode. Results show that TiO2 and SDC addition can reduce the sintering temperature and increase grain size. The ionic conductivity is 0.123 S cm−1 at 1000 °C. In addition, the thermal expansion coefficient at 1000 °C is 8.25 × 10−6 K−1. The current density of the cell is 439 mA cm−2 at 1.3 V and 1000 °C in solid oxide electrolysis cell.

Structural, morphological and electrical characterization of ceria-based nanostructured thin films obtained by ultrasonic spray pyrolysis

In this work, the synthesis and the structural, morphological and electrical characterization of Ce1−xSmxO2−δ solid solution, with x=0, 0.10, 0.15, 0.20, 0.25 and 0.30mol, are reported. Nanocrystalline, homogeneous, and adherent samarium doped cerium oxide thin films were deposited onto glass (Pyrex®) substrates by a simple and cost effective ultrasonic spray pyrolysis system, at a low substrate temperature of 450°C and further annealing treatment at 500°C for 2h. For all the samples, X-ray diffraction results showed the formation of single phase and well crystalline thin films, with cubic fluorite type structure. Scanning electron microscopy analyses showed homogeneous surfaces for all the samples; from SEM micrographs crystallite sizes were found to be in the range 23–37nm. From atomic force microscopy, surface roughness in the range of 20–95nm was measured and the formation of smooth films with an average grain size of 45nm was observed. For the best sample in the solid solution, high oxygen ion conductivity of 1.71×10−1Scm−1, at 450°C, was determined by impedance spectroscopy, with an activation energy of 0.93eV. Results suggest that these films may have a potential application as electrolytes in intermediate temperature solid oxide fuel cells, IT-SOFC.

Tunable transport property of oxygen ion in metal oxide thin film: Impact of electrolyte orientation on conductivity

Quest for efficient ion conducting electrolyte thin film operating at intermediate temperature (~600 °C) holds promise for the real-world utilization of solid oxide fuel cells. Here, we report the correlation between mixed as well as preferentially oriented samarium doped cerium oxide electrolyte films fabricated by varying the substrate temperatures (100, 300 and 500 °C) over anode/ quartz by electron beam physical vapor deposition. Pole figure analysis of films deposited at 300 °C demonstrated a preferential (111) orientation in out-off plane direction, while a mixed orientation was observed at 100 and 500 °C. As per extended structural zone model, the growth mechanism of film differs with surface mobility of adatom. Preferential orientation resulted in higher ionic conductivity than the films with mixed orientation, demonstrating the role of growth on electrochemical properties. The superior ionic conductivity upon preferential orientation arises from the effective reduction of anisotropic nature and grain boundary density in highly oriented thin films in out-of-plane direction, which facilitates the hopping of oxygen ion at a lower activation energy. This unique feature of growing an oriented electrolyte over the anode material opens a new approach to solving the grain boundary limitation and makes it as a promising solution for efficient power generation.

Shape-controlled fabrication of nanopatterned samarium-doped cerium oxide thin films using ultraviolet nanoimprint lithography

A shape-controlled method for the nanoscale patterning of cerium oxide thin films was demonstrated in this work. An ultraviolet-curable precursor-containing resin was newly developed for samarium-doped and undoped cerium oxide films, and ultraviolet nanoimprint lithography was employed for the nanopatterning. Various nanostructure shapes such as lines, circular pillars, and circular holes were fabricated, and a minimum feature width of 45nm was realized by patterning and subsequently shrinking the structures. The fabricated film was confirmed to be cerium dioxide, both undoped and doped with Sm. The effects of the annealing temperature on the crystallinity of the nanostructure and the controllability of the doping ratio were investigated. We believe that this work will provide a new path for preparing nanostructured cerium oxide for energy applications and a basic platform for analyzing the relationship between the structure and performance of size-controlled nanostructures.

Cubic fluorite phase of samarium doped cerium oxide (CeO2)0.96Sm0.04 for solid oxide fuel cell electrolyte

Nanocrystalline samarium doped cerium oxide of (CeO2)0.96Sm0.04 was synthesized by using a simple and environment-friendly sol–gel method via hydrolysis process. The synthesized cubic fluorite phase of (CeO2)0.96Sm0.04 solid electrolytes was confirmed by powder X-ray diffraction. Incorporation of samarium into the cerium lattice improved the redox ability of ceria. The fourier transform infrared (FT-IR) spectrum of samarium doped cerium oxide exhibits strong band below 700 cm−1 which is due to the δ(Ce–O–C) mode. The observed red shift in the UV–Vis absorption spectra confirmed the promoted electron–phonon interaction in samarium doped cerium oxide solid electrolytes. Scanning electron microscopy images of (CeO2)0.96Sm0.04 appeared as coral rock structure with slight agglomeration. Narrower particle distribution and the tightly packed surface morphology of the particles is a benefit for the efficient charge carrier formation. The electrochemical properties were examined by electrochemical impedance spectroscopy, cyclic voltammetry and chronoamperometry. Sm3+ ions involved a crucial role to decrease the ionic band between the Ce and O, which makes the oxygen flexible. Hence, (CeO2)0.96Sm0.04 solid electrolytes can be a suitable material for solid oxide fuel cell device applications.

The influence of the technological parameters on the ionic conductivity of samarium doped ceria thin films

Sm 0,20 Ce 0,80 O 2 powder was used for the formation of samarium doped cerium oxide (SDC) thin films using e-beam. Surface area of powder was 34.9 m 2 /g and particle size – 0.3-0.5 μm. Thin films were deposited using physical vapor deposition system on SiO 2 and Alloy 600 substrates. 2 A/s – 16 A/s growth rate and 20 °C – 600 °C substrate temperature were used during the deposition. Ionic conductivity investigation revealed that the maximum ionic conductivity (1.67 S/m) has the thin film deposited on 300 °C temperature substrate using 4 A/s growth rate. Minimum ionic conductivity (0.26 S/m) has thin film which was deposited on 20 °C temperature substrate using 8 A/s growth rate. Vacancy activation energies vary in 0.87 eV – 0.97 eV range. Furthermore the calculations of crystallite size revealed that crystallite size increases with increasing substrate temperature: from 7.50 nm to 46.23 nm on SiO 2 substrate and from 9.30 nm to 44.62 nm on Alloy 600 substrate. Molar concentration of samarium in initial evaporated material is 19.38 mol% and varies from 11.37 mol% to 21 mol% in formed thin films depending on technological parameters. DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5700

Structural and electrical study of samarium doped cerium oxide thin films prepared by e-beam evaporation

Samarium doped cerium oxide (Sm0.15Ce0.85O1.925, SDC) thin films were grown on the Alloy 600 (Fe–Ni–Cr) and optical quartz (SiO2) substrates using e-beam deposition technique. Formed SDC thin films were characterized using different X-ray diffraction (XRD) techniques, scanning electron microscope (SEM), energy-dispersive spectrometry (EDS) and impedance spectroscopy. The deposition rate of formed SDC thin films was changed from 2Å/s to 16Å/s.XRD analysis shows that all thin films have a cubic (FCC) structure and repeat the crystallographic orientation of the initial powders evaporated with different deposition rate and on different substrates. The crystallite size increases from 7.7nm to 10.3nm and from 7.2nm to 9.2nm on Alloy 600 substrate and optical quartz (SiO2) substrate respectively as the thin film deposition rate increases. SEM images indicate a dense and homogeneous structure of all formed SDC thin films.The ionic conductivity depends on thin films density and blocking factor. The best ionic conductivity (σg=1.34Sm−1 and σgb=2.29Sm−1 at 873K temperature, activation energy ΔEg=0.91eV and ΔEgb=0.99eV) was achieved for SDC thin films formed at 4Å/s deposition rate. It was found that the highest density (5.25g/cm3) and the lowest relaxation time in grain (τg =9.83×10−7s), and the lowest blocking factor (0.39) is in SDC thin films formed at 4Å/s deposition rate. The deposition rate influences the stoichiometry of the formed SDC thin ceramic films.

Role of iron addition on grain boundary conductivity of pure and samarium doped cerium oxide

The present paper reports the effect of iron doping (0.5, 1.5 mol%) on the densification and electrical properties of cerium oxide (CeO2) and 20 mol% samarium-doped cerium oxide (SDC) electrolytes for intermediate temperature solid oxide fuel cell (ITSOFC) applications. A single-step solution combustion method was used for doping and the resultant powder was compacted into green pellets and subsequently sintered at 1200 °C. X-ray diffraction (XRD) studies indicated the presence of a cubic fluorite CeO2 structure without the formation of a secondary phase and the stoichiometry was confirmed by X-ray fluorescence spectroscopy. In the as-compacted green pellets, the XRD peak position shifted to lower or higher angles depending on the ionic radii of the dopants due to lattice level mixing. Addition of iron resulted in smaller crystallite sizes ( 40 nm) after sintering. Densification was found to be higher (95%) in iron-doped samples than in bare samples (<90%) due to viscous flow sintering. Upon sintering the calculated strain value showed a lower value due to the segregation of iron from the lattice. Raman spectroscopic studies indicate that sintering marginally modifies the oxygen vacancy concentration in the SDC system, and found it to be higher than in CeO2. Addition of iron into the SDC improved the grain boundary conductivity 1.8 fold, but only a minor change was noticed for CeO2. The activation energy for the grain boundary conductivity was found to be lower for 1.5 mol% (1.06 eV) iron-doped SDC than for pure SDC (1.24 eV). Our results indicate that lattice level mixing of iron in SDC improves the density at relatively lower sintering temperatures and scavenges the grain boundary impurities, thereby increasing the grain boundary conductivity.

Texturing of pure and doped CeO2thin films by EBPVD through target engineering

In this paper, we report the effect of annealing temperature of target on the texture of thin films coated by electron beam physical vapor deposition method. Nanocrystalline cerium oxide (CeO2) and 20 mol% samarium doped cerium oxide (SDC) powders, compacted into pellets, were used as targets after annealing at 300, 500 and 800 °C. Grain size analysis of the target by X-ray diffraction showed a size range of 12–52 nm and 9–22 nm for CeO2 and SDC, respectively. Texture coefficient calculation from glancing incident X-ray diffraction showed a preferential orientation of (111) in CeO2 films. However SDC films exhibited (200) orientation grown at the expense of (111) which resulted in higher residual strain with annealing temperature. The pole figure analysis elucidated smaller in-plane misorientation in CeO2 than in SDC films. Under similar deposition conditions, difference in textured growth between CeO2 and SDC is primarily induced by vapor pressure modifications associated with the annealing temperature of the target. Raman and X-ray photoelectron spectroscopic studies of the films indicate the presence of higher oxygen vacancy concentration in SDC as well as a decrease in Ce3+ concentration with target annealing temperature.

Densification of Sm0.2Ce0.8O1.9 with the addition of lithium oxide as sintering aid

20 mol% samarium doped cerium oxide (Sm0.2Ce0.8O1.9, SDC) has one of the highest ionic conductivities as electrolyte for solid oxide fuel cell in intermediate temperature, but is restricted to commercial application for its poor densification behavior. The addition of 2 mol% Li2O in the Sm0.2Ce0.8O1.9 (SDC2) improves its maximum shrinkage rate from 4.6 × 10−3 min−1–1.1 min−1 at a heating rate of 10 °C min−1. The relative density of SDC2 achieves 99.5% at 898 °C and 3 °C·min−1, while it is only 82% for SDC at 1250 °C and 3 °C min−1. The grain boundary diffusion is the densification mechanism, and the mobility of grain boundary increases from 9.8 × 10−19 m3 N−1 s−1 of SDC to 4.2 × 10−17 m3 N−1 s−1 of SDC2 at 900 °C. The activation energy for densification as high as 5.5 ± 0.5 eV for SDC2 contributes to the formation of liquid phase in the grain boundary. The open circuit voltage of the cell using SDC2 as electrolyte as high as 0.78 V at 600 °Cunder solid oxide fuel cell (SOFC) working conditions demonstrates its promising for SOFC electrolyte.

Structural and optical study of samarium doped cerium oxide thin films prepared by electron beam evaporation

Samarium doped cerium oxide films were grown on the glass substrate using e-beam deposition technique and then characterized using different techniques: X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy and UV–visible spectroscopy measurements. XRD analysis shows that all the films have cubic structure and the crystallite size decreases from 18 to 13 nm as the samarium (Sm) concentration increases. The FE-SEM images indicate that all the films have columnar growth. UV–visible measurements reflect that the films have high transparency (>80%) in the visible region. From the Raman spectra, we have observed two peaks at 466 and 565 cm −1. The peak at 466 cm −1 is assigned to the F 2g mode of cerium oxide (CeO 2) whereas the peak at 565 cm −1 is due to the presence of the oxygen vacancies. The increase in the intensity of the peak at 565 cm −1 indicates that the oxygen vacancy increases with Sm doping.

Structural properties of Sm 3+ doped cerium oxide nanorods synthesized by hydrolysis assisted co-precipitation method

Cubic phase of 5% samarium doped cerium oxide nanoparticles was successfully synthesized by hydrolysis assisted co-precipitation method. The average grain sizes of the as-prepared and annealed (800 °C) samples were 12–16 nm respectively. The rod like morphology of the post annealed sample was revealed by transmission electron microscope (TEM). The nanoparticles exhibited the orange and red color emissions when excited at 330 nm. The as-prepared and annealed powders showed orange emission with maximum intensity at 574 nm which is the characteristic peak of the Sm 3+ ion corresponding to the magnetic dipole transition between the 4G 5/2 and 6H 5/2 states. Size dependent luminous intensity was observed from photoluminescence studies.

La 0.6Sr 0.4Co 0.2Fe 0.8O 3− δ cathodes infiltrated with samarium-doped cerium oxide for solid oxide fuel cells

Porous La 0.6Sr 0.4Co 0.2Fe 0.8O 3− δ (LSCF) cathodes are coated with a thin film of Sm 0.2Ce 0.8O 1.95− δ (SDC) using a one-step infiltration process. Examination of the microstructures reveals that small SDC particles are formed on the surface of LSCF grains with a relatively narrow size distribution. Impedance analysis indicates that the SDC infiltration has dramatically reduced the polarization of LSCF cathode, reaching interfacial resistances of 0.074 and 0.44 Ω cm 2 at 750 °C and 650 °C, respectively, which are about half of those for LSCF cathode without infiltration of SDC. The activation energies of the SDC infiltrated LSCF cathodes are in the range of 1.42–1.55 eV, slightly lower than those for a blank LSCF cathode. The SDC infiltrated LSCF cathodes have also shown improved stability under typical SOFC operating conditions, suggesting that SDC infiltration improves not only power output but also performance stability and operational life.