Effect Of Ce Doping Research Articles

Effect of Ce-doping on microstructure and electrical properties of LaAlO3 ceramics

A series of novel negative temperature coefficient (NTC) thermistor materials based on La1-xCexAlO3 (0 ≤ x ≤ 0.2) ceramics were synthesized via the solid-state route. X-ray diffraction results confirmed the successful doping of Ce in the La1-xCexAlO3 crystal and the formation of a good solid solution. Scanning electron microscopy results indicated that Ce doping is beneficial for grain growth and reduces the porosity of the samples. With the increase in the Ce doping amount, the average grain size increased from 2.1793 to 10.7344 μm, and densities of the ceramics increased from 93.15% to 99.26%. The temperature vs resistance curve indicated that Ce doping reduces the resistivity of LaAlO3 materials, while reducing the B200/1400 value of the LaAlO3 ceramic. For a doping amount of 0.2, the B200/1400 value of the LaAlO3 ceramic decreased from 18175.1 to 4897.7K, and the resistivity at 1000 °C decreased from 68971.87 to 1105.15 Ω cm. In addition, the La1-xCexAlO3 (0 ≤ x ≤ 0.2) series materials exhibited good linear NTC characteristics. X-ray photoelectron spectroscopy results revealed that the resistivity of the LaAlO3 materials decreased after Ce doping owing to the transformation between the Ce4+ and Ce3+ valence states，and the concentration of Ce3+ increased with the increase in the Ce doping amount. Ce3+ increases the concentration of oxygen vacancies, decreasing the resistance. Impedance analysis findings suggested that the resistance of the La1-xCexAlO3 (0 ＜ x ≤ 0.2) material mainly originates from the grain. These results indicate that Ce doping is an effective method to reduce the resistivity of LaAlO3. Consequently, La1-xCexAlO3 (0 ≤ x ≤ 0.2) is a promising material for NTC applications.

Ce-doping effect on dosimetric properties of mullite single crystals synthesized by the floating zone method

We synthesized the 0.1, 0.5, 1.0, and 1.5% Ce-doped mullite single crystals by the floating zone method and evaluated their photoluminescence (PL) and thermally stimulated luminescence (TSL) properties. The single-phase orthorhombic structure was confirmed in all the samples from powder X-ray diffraction patterns. The transmittance spectra of all the samples showed the absorption related to the 4f-5d transitions of Ce3+ ions and optical band gap of mullite. The Ce-doped mullite single crystals had the PL attributed to the 5d-4f transitions of Ce3+ ions. In TSL properties, TSL glow curves had the glow peaks at 250 and 370 °C, and TSL spectra heated at 250 and 370 °C had the peak at around 390 nm owing to the Ce3+ ions. TSL dose response functions showed linear response from 0.01 mGy to 10 Gy for the 1.0% Ce-doped mullite single crystal and from 0.1 mGy to 10 Gy for the 0.1, 0.5, and 1.5% Ce-doped ones. The 1.0% Ce-doped mullite single crystal could be used multiple times for dosimetry. In addition, the TSL intensity of the 1.0% Ce-doped mullite single crystal after 7 days from X-ray irradiation was about 82.4% from immediately one after X-ray irradiation.

Investigation on the microstructural, optical and magnetic properties of Ce doped ZnO nanorods

Surfactant free wet chemical route is employed to synthesize Zn1-xCexO (x = 0.01, 0.03 and 0.05) nanorods. Effects of Ce doping on the microstructural, optical and magnetic properties of the ZnO nanorods are reported. X-ray diffraction study revealed the hexagonal wurtzite phase of ZnO with formation of secondary phase corresponding to CeO2. Nanorod nature of the samples was confirmed from field emission scanning electron microscope micrograph. The systematic decrease of band gap from 3.192 to 3.177 eV with increasing Ce doping concentration from 1 to 5% was evidenced from UV–Visible characterization. The photoluminescence spectral feature confirms the presence of intrinsic defects like zinc, oxygen vacancies etc. The different functional groups were identified from Fourier transform infrared spectra. A very weak ferromagnetic ordering was observed in all the samples at room temperature. Our study suggested that the synthesized Ce doped ZnO nanorods could be useful for optical device applications in the UV region.

Microstructural characterization of cerium rich phases in new polycrystalline Co–Al–W-xCe superalloys

Cerium (Ce) plays an important role in enhancing the properties of Ni and Co-based alloys at high temperatures. However, its influence on the crystallization, microstructure, and properties of Co superalloys is not fully known. This work investigated the effect of Ce-doping on the as-cast microstructure of γ′-formed Co–Al–W alloys. Co–9Al–9W-xCe alloys (x = 0, 0.1, and 0.5) were synthesized and their microstructures were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). Al occupied interdendritic spaces and formed Th2Zn17-type structures. Introduction of Ce to Co–Al based alloys formed Ce-rich interdendritic precipitates, which do not dissolve upon heat treatment.

Effect of Ce doping on crystallite size, band gap, dielectric and antibacterial properties of photocatalyst copper oxide Nano-structured thin films

Copper oxide thin films doped with Ce3+ ions were prepared by a sol–gel dip-coating method. XRD patterns and FTIR spectroscopy disclosed dual-phase copper oxide (CuO-Cu2O) with Ce doping. Morphology of films changed from irregular grain structure to cuboids. The bandgap of thin films decreased with an increase in Ce dopant. AC conductivity decreased with doping of Ce up to 2% while an increase in Ce concentration to 5% enhanced it. Photocatalytic activity increases with an increase in cerium dopant percentage. The probe of the antibacterial activity displayed that 3 at. wt. % Ce-doped copper oxide exhibits the best bactericidal effect against four bacterial strains. The improved antibacterial activity of the Ce doped copper oxide can replace silver for wound dressings, bone implants, and dental fillings.

Structural analysis and oxygen defects in the partially oxygen-reduced T′-Pr2-xCexCuO4+δ with x = 0 and 0.15 powders at the normal state

Structural analysis and observation of the oxygen migration of Pr2-xCexCuO4+δ (PCCO) with Ce-doping concentration, x, of 0 and 0.15 powders are briefly studied through neutron diffraction (ND) patterns and x-ray absorption spectroscopy (XAS) spectrum in the extended x-ray absorption fine structure (EXAFS) range. The PCCO powders are synthesized using the chemical dissolved technique and time-dependent oxygen-reduction annealing in flowing Ar atmosphere. All powders show a stable PCCO phase with tetragonal T′-type crystal structure (space group of I4/mmm) for both the as-prepared and partially oxygen-reduced PCCO powders at room temperature. Occupancy of the apical oxygen, O(3), is detected higher in the doped powders due to Ce-doping effect and generally increases after the shorter-time oxygen-reduction annealing. The decrease of O(3) occupancy is observed for the longer-time reduction annealing process indicating a trace of oxygen migration and recovery of oxygen defect on CuO2 plane in the T′-structure. This study is essential to elucidate the mechanism of oxygen removal in the electron-doped cuprates.

Synergetic adsorption and photocatalysis performance of g-C3N4/Ce-doped MgAl-LDH in degradation of organic dye under LED visible light

Adopting a facile one-step solvothermal method, CN/MgAl0.80Ce0.20-LDH, a lamellate composite of graphitic carbon nitride (g-C3N4, CN) and Ce-doped MgAl-layered double hydroxide (LDH), was synthesized. Profiting from the combined effect of Ce-doping and CN-LDH composition, CN/MgAl0.80Ce0.20-LDH possesses large specific surface area (52.71 m2 g−1) and high separation efficiency of photogenerated charge. When used to remove organic dye Congo red (CR), the composite exhibits enhanced efficiency which can be attributed to the synergetic performance of adsorption and photocatalysis. As a result, ~49% CR (50 mg L−1) can be adsorbed by CN/MgAl0.80Ce0.20-LDH and the CR degradation efficiency exceeds 90% within 180 min under light-emitting diode (LED) visible light irradiation, which is much higher than that of pristine CN (48.77%). The augmented surface area and proliferated active sites benefit the increase of adsorption capacity. The enhanced photocatalytic performance can be attributed to the efficient transmission of photogenerated electrons and holes between CN and MgAl0.80Ce0.20-LDH. Electrochemical impedance spectroscopy (EIS) analysis and photoluminescence (PL) analyses confirmed the effective separation of photogenerated electron-hole pairs in CN/MgAl0.80Ce0.20-LDH, while electron spin resonance (ESR) results verified the derivation of superoxide radicals (·O2-) species amid CR photocatalytic degradation.

Synthesis of pure phase SmFeO3 orthoferrites via self-propagating sol-gel combustion synthesis and study of Ce doping effect on their ferroelectric properties

SmFeO3 (SFO) is a highly challenging rear earth orthoferrites system for future modern spintronics applications and data storage devices due to its outstanding dielectric and ferroelectric properties, among other RFeO3 members. In the present attempt, Ce doped SFO system with compositions Sm1-xCexFeO3 (where x = 0.02 to 1) is explored to reveal its structural and ferroelectrics behavior in view to check its suitability for data storage applications. The systems were synthesized by a sol-gel method based on glycine gel reaction. The structural features of the as-synthesized samples are fitted by Rietveld refinement of x-ray diffraction patterns, which confirms an orthorhombic phase with pbnm space group. Temperature driven ferroelectric properties of Sm1-xCexFeO3 (where x = 0.02 to 1) were studied. Ce doped SmFeO3 indicates a reduction in losses and leakage current by Ce doping, suggesting that it is a promising material to explore as room temperature multiferroics.

Ce supported Al2O3 nanoparticles synthesized by coprecipitation method; morphology and optoelectronic study

In this research, ceria (Ce)- doped alumina (Al2O3) nanoparticles (NPs) were fabricated in different level of cerium using coprecipitation method. To characterize the morphology, crystal structure and optical properties, the FESEM, XRD, TEM, UV-DRS and FTIR analyses were performed. The structure analysis of undoped samples showed the multiple phases of γ, δ and θ–alumina, and the structure remained unchanged when cerium atom was doped into the alumina. The morphology and structure studies were carried out to investigate the effect of Ce doping on the polycrystalline alumina nanoparticles. The optical analysis was also done to study of the bandgap energy of the Al2O3 NPs. The novelty of this work is the synthesis of Ce-doped Al2O3 NPs with new precursors and improving their optical properties.

Investigation of Ce doped BaTiO3 compound for optoelectronic devices

The full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT) is employed to probe the optical and electronic features of Ba1-xCexTiO3 (x = 0%, 5.55%, 12.5%, 25% and 50%) perovskite oxides. The effect of Ce doping on the band structure (BS) and optical spectra of cubic BaTiO3 compound has been explored. The outcomes of this work unveil the indirect-band semiconducting nature of Ba1-xCexTiO3(x = 0%), which becomes direct after Ce doping. Moreover, the width of band gap (Eg) narrows with the upsurge of Ce concentration in BaTiO3. The optical behavior of Ba1-xCexTiO3 compounds is estimated through refractive index, reflectivity, dielectric constant, optical conductivity and absorption coefficient. The controlled reduction in Eg of BaTiO3 with rise in concentration of Ce is a useful tool to make this compound promising for optical and optoelectronic devices.

Pure and cerium-doped ZnO nanorods grown on reticulated Al2O3 substrate for photocatalytic degradation of Acid Red 88 azo dye

Pure and Ce-doped ZnO photocatalyst nanorods were both grown on α-Al2O3 ceramic foams manufactured using a polymeric sponge replication technique. A three-dimensional network of α- Al2O3 struts which served as the substrate for the photocatalyst material was first seeded via dip coating. The seed-mediated synthesis of ZnO nanorods with controlled lengths and diameters was then carried out at low temperature (∼95 °C) by chemical bath deposition (CBD). Their morphologies and crystallographic orientations were verified using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The effect of Ce-doping on the optical properties of the ZnO nanorods was investigated by ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopies. There was a modification in the band-gap structure with the incorporation of cerium atoms in the ZnO matrix as observed by the partial redshift at the absorption edges and by the blue and green light emissions. Color removal efficiencies of the samples were evaluated under UVA and visible light irradiations over the photocatalytic degradation of Acid Red 88 (AR88) azo dye molecules dissolved in water. Enhanced degradation rates were achieved for the Ce-doped samples compared to those of the pure ones. Similarly, the extend of mineralization (i.e., total organic carbon (TOC) removal) reached the maximum value of 54% for the Ce-doped samples under UVA light. According to the scavenging experiment results, it was found that the most effective radical involved in the present photocatalytic degradation reactions was the superoxide anion (·O2−).

Microwave rapid fabrication of cerium/cobalt nickel sulfide electrode materials for high performance supercapacitors

In this work, a novel electrode materials of cerium/cobalt nickel sulfide (Ce/CoNi2S4) was synthesized by a one-step microwave approach. The Ce doping effect has been an efficient method to increase the rate properties and specific capacitance of the supercapacitor. When the current density is 1 A g−1, the specific capacitance of the CoNi2S4 electrode is 1988 F g−1, but when a small amount of rare earth (cerium nitrate hexahydrate) was doped, the optimized Ce/CoNi2S4 electrode exhibits a great specific capacitance of 2408 F g−1 at 1 A g−1 and excellent cycling stabilities (86% retention after 10000 cycles and 71% retention after 20000 cycles). In addition, the Ce/CoNi2S4 nanoflower shows excellent performance for aqueous asymmetric supercapacitor, and the energy density is as high as 70.4 Wh kg−1 when the power density is 750 W kg−1, and 52.1 Wh kg−1 when the power density is 7500 W kg−1. The Ce/CoNi2S4 electrode materials were synthesized by household microwave oven, which can not only realize the simple and efficient synthesis of materials, but also can realize the improvement of the properties of sulfide materials. This rare earth doped sulfide is a new concept in the synthesis design, and can also be apply to the synthesis of other materials, which has a certain guiding effect on the improvement of the performance of electrode materials in supercapacitors.

Effect of Ce doping on the structural, optical, and photovoltaic properties of TiO2 based dye-sensitized solar cells

In this research, the sol-gel technique has been used for the preparation of titanium dioxide (TiO2), 1% cerium doped titanium dioxide (Ce–TiO2), 1% Ce–TiO2/TiO2, and TiO2/1% Ce–TiO2 films. XRD pattern verified that all the films consist of TiO2 anatase phases. The crystallite size of bilayer film is larger than that of a single deposited film. According to UV–Visible spectroscopy, the film Ce–TiO2/TiO2 has low band gap energy (Eg) value of 3.28 eV. The DSSCs of these films are fabricated with N719 dye and iodide/tri-iodide electrolyte. Various parameters including short circuit current density, open circuit voltage, fill factor, and efficiency of the cells are determined through J-V curves. The results exhibited that 1% Ce–TiO2/TiO2 film has achieved a maximum efficiency of about 3.08%.

Effect of Ce doping on the structural, transport and magnetic properties of Sr2IrO4 epitaxial films

Sr2IrO4 is predicted to be superconducting and has received extensive attention in the field of high-temperature superconducting. Bulk Sr2IrO4 can be converted to a metallic state by slight chemical doping. Here we studied the structure, morphology, transport and magnetism of (Sr1−x Ce x )2IrO4 (x= 0, 0.0125, 0.025, 0.05) epitaxial films grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 substrates. Unlike the bulk Sr2IrO4 material, the doped Sr2IrO4 epitaxial film maintains a wide range of Mott variable-range hopping characteristics in transport. Meanwhile, the magnetic properties and Raman characteristic peaks of the doped films become weakened, and the degree of weakening is proportional to the doping concentration. These observations can be attributed to the localization caused by disorder after Ce doping and the presence of structural defects. The epitaxial strain may result in important differences between Sr2IrO4 epitaxial thin films and bulk single crystals.

The effect of Ce-doping on the structural, electronic and magnetic properties of LiAl5O8: A first-principles study

The host matrix LiAl5O8 doped with Ce3+ has great potential for applications in LED (light-emitting diode) and scintillators. In this work, we use ab initio calculations based on the density functional theory (DFT) to describe the effects caused by Ce dopant on the structural, electronic and magnetic properties of LiAl5O8. To evaluate where the dopant is inserted, we consider two calculation configurations: the Ce ion is inserted in the tetrahedral site (8c) and in the octahedral site (12d). To evaluate which charge of the dopant makes the system more stable, we performed the simulations considering the neutral system q ​= ​0, removing an electron q ​= ​+ 1 and adding an electron q ​= ​- 1. The Kohn-Sham equations were solved considering correlation and exchange effects described by the generalized gradient approximation (GGA) with PBE parameterization and GGA ​+ ​Ueff (Ueff ​= ​2.0 ​eV, 2.5 ​eV, and 3.0 ​eV). The lattice parameters and atomic positions have been optimized and then the local structure around the defect has been determined. Through the Bader analysis, we determine the dopant charge that makes the system more stable. The incorporation of the Ce ion in the host matrix leads to the formation of an occupied 4f state inside band gap, corresponding to a 4f electron of Ce3+. The occupied 4f state is located at 3.25 ​eV above the top of the matrix valence band. We obtained a value of approximately +1μB for the total spin magnetic moment in the unit cell for the replacement of Al3+ by Ce3+ at the octahedral site.

Ce doping induced modifications in structural, electrical and magnetic behaviour of hematite nanoparticles

In this paper, we investigate effects of Ce-doping on the structural, electrical and magnetic properties of Fe2-2xCe2xO3 samples synthesized by sol–gel method by varying the composition as (x = 0.00, 0.02, 0.05, 0.08, 0.10). The recorded XRD pattern of synthesized powder samples indicates the formation of hematite phase up to the dopant concentration x = 0.05, thereafter a further increase in doping concentration leads to the existence of secondary phase of cerium oxide (CeO2) along with the pure phase of hematite. Moreover, XRD results are well supported by FTIR and Raman spectroscopy observations. Variation in grain size as well as the grain growth as revealed from FE-SEM micrographs may be possibly due to Ce ions having different ionic radii than that of the host Fe3+. DC electrical resistivity variation with temperature in the range 150–400 K, reveals the enhancement in electrical conductivity due to the increase of Ce-doping content. Magnetic hysteresis measurements carried out at room temperature (300 K) with a maximum applied field of ±10000Oe reveal that the magnetic parameters i.e. remnant magnetization (MR) and coercivity (HC) of Ce2xFe2-2xO3 increase up to the doping concentration of x = 0.02, thereafter a significant random variation is observed.

Effect of Ce doping on the catalytic performance of xNiCeOy@SiO2 catalysts for dry reforming of methane

AbstractA series of xNiCeOy@SiO2 catalysts with different cerium contents were prepared by hydrothermal coprecipitation and Stöber method. The results of catalytic performance showed that 15NiCeOy@SiO2 has the best catalytic activity with the methane conversion of 81.1% and the specific activity of the catalyst (the amount of methane converted per mol Ni per minute) of 1.14. 10NiCeOy@SiO2 exhibits the highest stability, with the methane conversion remaining unchanged within 40 h. Compared with the undoped Ni@SiO2 catalyst, the enhancement of the activity can be attributed to the reduction of the Ni particle size due to the doping of Ce, which enabled more exposure of active species. Meanwhile, the oxygen vacancies originating from extrinsic defects of ceria increase the reaction rate of activated carbon and CO2, inhibit carbon deposition, and accelerate the structure stability.

Effect of water treatment and Ce doping of Pt/Al2O3 catalysts on Pt sintering and propane oxidation

The effect of Ce doping and pretreatment of Pt/Al2O3 on its catalysis of propane oxidation was investigated after aging the catalysts. The Ce amount and pretreatment conditions were varied, and the propane oxidation activity was measured. The properties of the catalysts were investigated by means of XRD, STEM-EDX, FT-IR, and H2-TPR. The size of the Pt nanoparticles (PtNPs) decreased for water-treated catalysts doped with a small amount of Ce, suggesting that water treatment of Ce-doped catalysts inhibits Pt sintering. The minimum PtNP size was obtained with ca. 3.6 wt% of Ce. The Ce species with less than 3.6 wt% existed in a dispersed state, whereas above this value, CeO2 particulates co-existed. The propane oxidation temperature of the water-treated catalysts was lowered to an extent that depended on the Ce content. This tendency is consistent with the PtNP size in the catalysts. It is considered that highly dispersed Ce species take a primary role in promoting propane oxidation on PtNPs. The reduction temperature of Ce species on water-treated catalysts was lower than that of untreated catalysts, probably owing to a stronger interaction between Pt and Ce, demonstrated by FT-IR measurements. The increased reducibility of Ce species may be the reason for the improved oxidation activity of the catalysts.

ErB6 ve Ce katkılı ErB6 Yapılarının Optiksel, Elektronik, Mekanik ve TermalÖzellikleri: Hesaplamalı MalzemeÇalışması

Erbiyum hexaboride is one of the heavy rare aearth hexaborides that indicate superior chemical and physical properties. In this study, Erbiyum hexaboride and Ce doped Erbium hexaboride crystal structures have been investigated systematically employing ab initio material modeling. The effects of Ce doping (wt.%10) on Erbiyum hexaboride structure in terms of optical, thermal, mechanical and electronic properties including band properties, enthalpy of formation energies and bulk modules were investigated. Results show that the Ce doping leads to an increase in the bandgap of the structure. Furthermore, the bulk modules calculations show that Ce doping to the structure leads to an increase in mechanical properties.

Quantum chemistry study of SCR-NH3 nitric oxide reduction on Ce-doped γFe2O3 catalyst surface

The doping of Ce on γ-Fe2O3 catalyst surface can improve the NO removal catalytic activity and widen the temperature window of activity. However, the mechanism of promoting the De-NOx activity of γ-Fe2O3 catalyst by Ce doping has not been revealed. In this paper, therefore, the doping of Ce on γ-Fe2O3(001) surface and the adsorption behavior of NH3 and NO as well as the reaction pathway were studied by the density functional theory (DFT). The results show that the doping of Ce on γ-Fe2O3(001) surface can lead to the migration of electrons on the surface of catalyst and cause the dislocation of the surface lattice, so as to improve the surface acid activity. Thus, the Ce doping can increase the adsorbed energy of the modified γ-Fe2O3 catalyst to NO and NH3 and decrease the activation energy barrier of the rate determining step in SCR reaction. Furthermore, the effects of Ce doping will change with the concentration of the Ce doping, and the excellent SCR De-NOx efficiency will be obtained in the optimal doping amount. On the other hand, O2 makes an important effect. Which makes the activation energy barrier of the rate determining step under aerobic condition lower than that under anaerobic conditions, causes the surface active O to react with NO to form NO2 and perform a rapid SCR reaction. The Ce doping can promote the dissociation of O2 on the active cation site and reduce the activation energy barriers of above steps. Accordingly, the doping of Ce on γ-Fe2O3 catalyst surface can improve the SCR process.