Narrow Results

The structure and properties of the nanosized ${\mathrm{\text{CeO}}}_2$ under high pressure have been investigated by synchrotron X-ray diffraction in the diamond anvil cell combined with the first-principle methods based on density functional theory. The experimental data demonstrate that nanosized ${\mathrm{\text{CeO}}}_2$ is highly stable upto 31.3 GPa and bulk modulus is $213\pm 3$ GPa. The calculated results by $\mathrm{\text{LDA}}+\mathrm{\text{U}}$ indicate that ${\mathrm{\text{CeO}}}_2$ undergoes structural transition from cubic fluorite-type structure to orthorhombic $\alpha$-${\mathrm{\text{PbCl}}}_2$-type structure at 20 GPa. The indirect band gap $(\mathrm{\text{R}}\to \mathrm{\text{G}})$ is 1.89 eV and increases with the increasing pressure while it suddenly reduces to 1.62 eV at transition pressure. The transition pressure calculated by GGA is 40.3 GPa.

The effects of Ti and Zr doping concentrations on the mechanical properties and electronic structure of the reduced Ce${}_{1-x}$M${}_x$O${}_{1.785}$ were studied. The calculated results show that elastic moduli of Ce${}_{1-x}$Ti${}_x$O${}_{1.875}$ decreased, while those of Ce${}_{1-x}$Zr${}_x$O${}_{1.875}$ increased. Ce${}_{0.625}$Ti${}_{0.375}$O${}_{1.875}$ that undergoes structural transformation at 37.5 at.% Ti. Ce${}_{1-x}$M${}_x$O${}_{1.875}$ is ductile material. The degree of anisotropy of Ce${}_{1-x}$Ti${}_x$O${}_{1.875}$ decreased sharply at 25 at.% Ti, while that of Ce${}_{1-x}$Zr${}_x$O${}_{1.875}$ almost unchanged with the increase of Zr concentration. Ti and Zr doping has little effect on the electronic structure of the unreduced Ce${}_{1-x}$M${}_x$O₂. Ti and Zr doping reduced the formation energy of O vacancy, and Ti doping was more conducive to the formation of O vacancy. The density of states of the reduced Ce${}_{1-x}$M${}_x$O${}_{1.875}$ exhibited spin splitting and was magnetic. Zr atom transferred 0.24–0.27 e more than Ti atom to the nearest O atoms, and Zr–O bond has stronger covalency and higher bond energy.

In this paper, the structural, electronic, optical, and mechanical properties of the hexagonal Ceria CeO₂ have been studied with hybrid functionals. The rare-earth oxide compound exhibits a $\mathrm{\Gamma }-M$ indirect bandgap, with a bandgap energy of 2.706 eV. The electronic bandstructure has been described in detail in terms of orbital states. The rare-earth Ce f orbital contributes to the conduction band and transitional Ce d, O s electron orbitals to the valence bands. Our optical spectra also fully explain the structural and electronic properties of the material. (i.e. atomic-bonding, density or capacity inside Cerium oxide system, and the excitation of electrons to transfer from valence O 2p to conduction Ce f orbitals, leading to orbital hybridizations, etc.). Finally, our elastic coefficients verify the mechanical stability of our Ceria system. Our bandgap energy found is in excellent agreement with the experimental data. A high optical absorption coefficient of up to $1\times 10^5$ cm${}^{-1}$ is found, indicating a good material absorption within the ultraviolet C (UVC) range. The findings of this work would be beneficial to both theoretical and experimental research works to explore the potential applications of CeO₂ in optoelectronics devices.

In this study, the WIEN2k code, utilizing the full potential linearized augmented plane wave (FPLAPW) approach within the framework of density functional theory (DFT), explicitly employing the PBEsol approximation, is employed to investigate the fundamental properties of W-doped and (Mo, W) co-doped cubic CeO₂. Herein, lattice constants, bulk modulus and cell volumes were evaluated for structural properties. The total density of states (TDOS) for various doped and co-doped CeO₂ systems was used to explain the origin of magnetic behavior. The band structure (BS) calculations show that the doped and co-doped materials exhibit semiconductor behavior with a direct bandgap in both spin channels. The calculated total spin magnetic moments of W/CeO₂ and (Mo, W)/CeO₂ alloys are 2.002${\mu }_B$ and 4.007${\mu }_{B,}$ respectively.

Furthermore, the optical absorption shows absorption peaks in the visible range and a redshift. As a result, adding molybdenum and tungsten additives improves the electro-optical properties of previous materials.

CeO₂ thin films were deposited on Si, Al, Ti–6Al–4V alloy, Si₃N₄ and glass substrates by magnetron sputtering at room temperature. Growth of CeO₂ films on Si and Si₃N₄ and effect of annealing were investigated by XRD, FESEM and AFM. Interaction between deposited CeO₂ films and Si, Al, Ti–6Al–4V alloy, Si₃N₄ and glass substrates was investigated by XPS. XRD studies show that films are oriented preferentially to (200)-direction of CeO₂ and no significant change is observed in the XRD patterns of films after heat treatment. CeO₂ film on Si₃N₄ exhibits rough morphology, whereas very fine morphology is observed in CeO₂ film on Si. CeO₂ film on Si shows lower roughness in relation to that on Si₃N₄ as demonstrated by AFM studies. XPS results show that Ce is present as both +4 and +3 oxidation states in CeO₂ film deposited on Si and Al substrates, whereas Ce⁴⁺ is the main species in CeO₂ films deposited on Ti–6Al–4V alloy, Si₃N₄ and glass substrates. Ce3d, Si2p and O1s core level spectra demonstrate that Ce₂O₃ or cerium silicate and SiO_x type of species are formed at the interface of CeO₂ and Si. Similarly, formation of interfacial species like Ce₂O₃ or cerium aluminate is evident in CeO₂ film on Al as demonstrated by XPS studies. On the other hand, interfacial reactions between CeO₂ and Ti–6Al–4V alloy, Si₃N₄ and glass substrates are limited in the respective films.

This paper presents a first principles calculation of the structure and electronic properties of four crystal GeO₂ structures and two rare-earth element oxides CeO₂ and La₂O₃. A GGA was used to optimize structures and calculate band structure and density of states (DOS). It is found that La₂O₃ has the largest band gap (4.19 eV) among all the six structures, which also means it is the best insulator among them. When it comes to four crystal GeO₂ structures, which were calculated to make a comparison with two insulators CeO₂ and La₂O₃, we found the q-GeO₂ and b-GeO₂ are more likely to work as the dielectrics used in MOS devices than the other two crystalline forms. Three of the four GeO₂ forms have larger band gap than that of CeO₂ (2.09 eV), which indicates CeO₂ is not a wise choice when deposited directly on the surface of Ge substrate.

We have used the co-precipitation technique to synthesize nanocrystalline Co-doped CeO₂ dilute magnetic semiconductors with Co concentrations ranging from 0.0–0.07. X-ray diffraction patterns (XRD) demonstrate that all the samples display single phase cubic structure without any impurity phase. Average particle sizes calculated from XRD and transmission electron microscopy (TEM) studies showed a gradual decrease with increase in Co ions concentration. UV–visible optical spectroscopy measurements reflect an energy band gap, which decreases with the increasing concentration of dopant (x ≤ 0.03). Raman spectra show an intensity loss of classical CeO₂ vibration modes, which is an indication of considerable structural modifications and disorder in CeO₂ lattice. Magnetic measurements revealed that all the samples exhibit a weak ferromagnetism at room temperature.

The catalytic performance of ceria oxide (CeO${}_2)$ was greatly influenced by the materials’ structure and surface area. In this paper, CeO₂ porous nanospheres (PNS) with tunable pore and sphere sizes were synthesized by a solvothermal method using diethylene glycol as reaction media. All the as-synthesized CeO₂ PNS presented good adsorption capacity for methyl orange, which makes them potential application in waste water treatment conveniently and economically. The control over the sphere and pore sizes of CeO₂ PNS was achieved by regulating the volume of water bubble in the reaction system, which supplied limited room for the assembling of preformed CeO₂ small nano-precursors.

Eu${}^{3+}$/Tb${}^{3+}$ co-doped nanocomposite containing CeO₂ nanocrystals was successfully prepared by an in situ sol–gel polymerization approach. High-resolution transmission electron microscopy demonstrated the homogeneous precipitation of CeO₂ nanocrystals among the polymethylmethacrylate (PMMA) matrix. The thermal stability and UV-shielding capability of the obtained nanocomposite were improved with increase of CeO₂ content. The tuning of the emissive color from green and yellow to red can be easily achieved by varying the dopant species and concentration. These results suggested that the obtained nanocomposite could be potentially applicable in transparent solid-state luminescent devices.

A facile strategy is described for general synthesis of MCo₂O₄@CeO₂ ($\mathrm{\text{M}}=\mathrm{\text{Ni}}$, Cu, Zn, Mn) core@shell nanospheres. First, uniform M,Co–glycerate were prepared and served as precursor to produce MCo₂O₄ spheres by calcination, followed by a reflux process to obtain MCo₂O₄@CeO₂ core@shell spheres. As expected, due to the synergetic effect at the interface between the two components, most of the as-prepared MCo₂O₄@CeO₂ core@shell spheres exhibited enhanced catalytic activities toward CO oxidation compared with the corresponding MCo₂O₄ spheres and CeO₂ nanoparticles.

Water electrolysis is one of the most feasible ways to utilize clean and renewable energy sources in the form of hydrogen energy. However, the anodic oxygen evolution reaction (OER) is a slow kinetic process, so it is of great significance to develop efficient oxygen evolution catalysts (OECs). Many studies have shown that Ce plays an important role in high-performance transition-metal-based OECs. We discuss and summarize possible causes for the improved OER activity and stability with emphasis on the hybrids of cerium and transition metals, including cerium-doped catalysts, ceria-support catalysts and ceria-loaded catalysts. Finally, current challenges for the Ce-containing catalysts are identified, pointing to the future directions for propelling the water electrolysis research.

For the first time, CeO₂ nanoparticles (NPs) were synthesized via green solution combustion method using Ocimum sanctum Linn (Tulsi) leaves extract as a reducing agent. The as-formed and calcined (500^∘C for 3h) CeO₂ NPs were characterized with different techniques. The Bragg reflections clearly indicate that the formation of cubic fluorite structure with crystallite size was found to be 10nm. The surface morphology of as-formed and calcined sample is made up of large number of irregular shaped NPs. However, agglomeration of the NPs is more in calcined sample. The estimated direct energy band gap from Tauc’s relation was found to be 2.92eV and 2.87eV for the as-formed and calcined sample, respectively. Photoluminescence spectra, CIE and CCT values clearly indicate that the present nanophosphor might find an application in display technology. Antifungal and anticancer studies show that CeO₂ NPs are noncytotoxic against fungus and cancerous cells. Whereas, electrochemical studies show that the synthesized CeO₂ NPs show redox peaks and pseudo capacitance and hence it finds importance in supercapacitor applications.

This study investigates the electronic and structural properties of heterojunctions formed by mono-/bi-layers of graphene on a cerium oxide (CeO₂) substrate. By utilizing first-principles calculations, we analyze the effects of the CeO₂ substrate on graphene’s electronic structure and interfacial properties. The presence of the CeO₂ substrate induces significant modifications in the band structure, including the formation of interface states and changes in the bandgap. The interfacial bonding and lattice matching play crucial roles in determining the heterojunction’s electronic behavior. Furthermore, we examine the charge transfer phenomena and its influence on electrical conductivity and carrier mobility. This research provides insights into the design and optimization of graphene-based devices on CeO₂ substrates for potential electronic and optoelectronic applications.