scholarly journals Cerium oxide based nanometric powders: synthesis and characterization

2007 ◽  
Vol 39 (3) ◽  
pp. 301-308 ◽  
Author(s):  
M. Ninic ◽  
S. Boskovic ◽  
M. Nenadovic ◽  
S. Zec ◽  
K. Voisavljevic ◽  
...  
Keyword(s):  
Rare Earth ◽  
Cerium Oxide ◽  
Solid Solutions ◽  
Oxygen Vacancies ◽  
Total Concentration ◽  
Lattice Parameter ◽  
Lattice Parameters ◽  
Synthesis And Characterization ◽  
In Doping ◽  
Host Compound

Nanometric powders of solid solutions of cerium oxide were obtained by a modified glycine nitrate procedure. Solid solutions of the host compound CeO2 with one or more dopants in the lattice were synthesized. Rare earth cations (Re=Yb, Gd and Sm) were added to ceria in total concentration of x= 0.2 that was kept constant. The criterion in doping was to keep the value of lattice parameter of ceria unchanged. The lattice parameters were calculated by using the model that takes into account the existence of oxygen vacancies in the structure.

scholarly journals Studies on Structural and Morphological Properties of Multidoped Ceria Ce0.8Nd0.0025Sm0.0025Gd0.005Dy0.095Y0.095O2-δ(x=0.2) as Solid Solutions

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Marija Stojmenović ◽  
Maja C. Pagnacco ◽  
Vladimir Dodevski ◽  
Jelena Gulicovski ◽  
Milan Žunić ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Solid Solutions ◽  
Room Temperature ◽  
Oxygen Vacancies ◽  
Room Temperature Ferromagnetism ◽  
Fluorite Structure ◽  
Lattice Parameter ◽  
Morphological Properties ◽  
Fluorite Type ◽  
Potential Improvement

The nanopowdery solid solutions of multidoped ceria Ce0.8Nd0.0025Sm0.0025Gd0.005Dy0.095Y0.095O2-δ(x=0.2) with the fluorite type crystal structure of CeO2were synthesized for the first time. Two synthesis procedures were applied: the modified glycine-nitrate procedure (MGNP method) and room temperature self-propagating reaction (SPRT method). All nanopowders were characterized by XRPD analysis, Raman spectroscopy, low temperature nitrogen physisorption, TEM, and SEM methods. According to the XRPD and Raman spectroscopy results, single phase solid solutions of fluorite structure were evidenced regardless of the number of dopants and synthesis procedure. Both XRPD and TEM were analyses evidenced nanometer particle dimensions. The SPRT method results in obtaining sample with higher specific surface area, smaller crystallite and particles sizes, and the same values of the lattice parameter in comparison to pure CeO2. Raman spectroscopy was confirmed to the oxygen vacancies introduced into the ceria lattice when Ce4+ions were replaced with cations (dopants) of lower valence state (3+), which may indicate the potential improvement of ionic conductivity. Additionally, the presence of oxygen vacancies in the lattice ceria, as well as very developed grain boundaries, gives a new possibility for potential application of obtained nanopowders in the area of room temperature ferromagnetism as spintronics.

scholarly journals Raman Study of Nanocrystalline-Doped Ceria Oxide Thin Films

Coatings ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 432 ◽  
Author(s):  
Nursultan Kainbayev ◽  
Mantas Sriubas ◽  
Darius Virbukas ◽  
Zivile Rutkuniene ◽  
Kristina Bockute ◽  
...  
Keyword(s):  
Thin Films ◽  
Rare Earth ◽  
Cerium Oxide ◽  
Oxygen Vacancies ◽  
Raman Shift ◽  
Size Factor ◽  
Doped Ceria ◽  
X Ray ◽  
Sio2 Substrate ◽  
Lower Frequencies

Samarium-doped ceria (SDC) and gadolinium-doped ceria (GDC) thin films were formed by e-beam vapor deposition on SiO2 substrate, changing the deposition rate and substrate temperature during the deposition. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-Ray spectrometry (EDS) were employed in order to investigate the structure ad morphology of the films. A single Raman peak describing the structure of undoped CeO2 was observed at a frequency of 466 cm−1. Doping of cerium oxide with rare-earth elements shifted the peak to lower frequencies (for Sm—462 cm−1). This shift occurs due to the increased number of oxygen vacancies in doped cerium oxide and it depends on the size and concentration factor of the dopant. It was found that wavenumbers and their intensity differed for the investigated samples, even though the peaks resembled each other in shape. The indicated bands for doped ceria originated as a result of the Raman regime (F2g) of fluorite dioxide associated with the space group (Fm3m). The observed peak‘s position shifting to a lower frequency range demonstrates the symmetric vibrations of oxygen ions around Ce4+ ions in octahedra CeO8. Raman shift to the lower frequencies for the doped samples has two reasons: an increase in oxygen vacancies caused by doping cerium oxide with rare-earth materials and the size factor, i.e., the change in frequency Δω associated with the change in the lattice constant Δa.

LATTICE PARAMETERS OF MELILITE SOLID SOLUTIONS AND A RECONNAISSANCE OF PHASE RELATIONS IN THE SYSTEM Ca2Al2SiO7 (GEHLENITE) – Ca2MgSi2O7 (AKERMANITE) – NaCaAlSi2O7 (SODA MELILITE) AT 1 000 kg/cm2 WATER VAPOR PRESSURE

1965 ◽  
Vol 2 (6) ◽  
pp. 596-621 ◽  
Author(s):  
A. D. Edgar
Keyword(s):  
Solid Solutions ◽  
Water Vapor Pressure ◽  
Lattice Parameter ◽  
Lattice Parameters ◽  
Phase Relations ◽  
Ray Method ◽  
Subsolidus Phase ◽  
X Ray ◽  
Complete Solid Solution ◽  
Temperature Lattice

The extent of melilite solid solutions has been determined for the systems gehlenite–soda melilite, akermanite–soda melilite, and gehlenite–akermanite–soda melilite at 800 °C and 1 000 kg/cm2[Formula: see text] Approximately 50 weight % NaCaAlSi2O7 will form melilite solid solutions with both gehlenite and akermanite but the extent of complete solid solutions in the gehlenite–akermanite–soda melilite system is very limited at this temperature. Lattice parameter determinations of melilite solid solutions indicate that there is a small but significant change in both a and c parameters with increasing soda melilite in the gehlenite–soda melilite system. In the gehlenite–akermanite–soda melilite system, although the range of complete solid solution is very limited, melilites form more than 90% of the products in most compositions and their lattice parameters can be correlated approximately with their bulk compositions, A rapid X-ray method has been developed to determine the approximate compositions of melilites in this system. Comparison is made between the synthetic samples and natural melilites.A reconnaissance of subsolidus phase relations indicates that phase relations are very complex and that only over a very small compositional range can these systems be considered binary or ternary. These studies also indicate that the relations reported by Nurse and Midgley in 1953 should probably be modified. Although the composition NaCaAlSi2O7 does not synthesize only a melilite under the conditions used in this study, it is believed that this is the correct composition of the sodium-bearing end-member.

Lattice Spacings in Some Transition Metal Terminal Solid Solutions

1962 ◽  
Vol 6 ◽  
pp. 121-135 ◽  
Author(s):  
Henry Chessin ◽  
Sigurds Arajs ◽  
D. S. Miller
Keyword(s):  
Transition Metal ◽  
Size Effect ◽  
Elasticity Theory ◽  
Solid Solutions ◽  
Calculated Data ◽  
Lattice Parameter ◽  
Lattice Parameters ◽  
Classical Elasticity ◽  
Atomic Size ◽  
Classical Elasticity Theory

AbstractThe lattice parameter-composition curves for several nickel solid solutions and for some chromium and. iron solid solutions are discussed. It is shown that the size effect may be the predominating influence on the change of lattice parameters in these systems. This is demonstrated by comparing observed and calculated data employing various methods. A new scheme for evaluating the atomic size in solid solutions is proposed, based on regarding the atom, as an incompressible core surrounded by a smeared-out compressible volume. The suggestion that classical elasticity theory may be used as a basis for understanding the size effect in solid solutions is justified by examination of the Ag-Pd system for additions of Ag from 0 to 100 at. %.

The Effect of Substituting Ga for Alon Crystal Structure of Phosphors MAl 2Si2O8: Eu2+ (M= Ca, Sr, Ba)

2022 ◽  
Vol 905 ◽  
pp. 91-95
Author(s):  
Fei Wang ◽  
Hui Hui Chen ◽  
Shi Wei Zhang
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Cell Volume ◽  
Solid Solutions ◽  
Solid State Reaction ◽  
Unit Cell Volume ◽  
Lattice Parameter ◽  
Unit Cell ◽  
Lattice Parameters ◽  
Reductive Atmosphere

A series of luminescence phosphors M0.955Al2 –xGaxSi2O8∶Eu2+ (M=Ca, Sr, Ba, x = 0~1.0) were prepared via solid-state reaction in weak reductive atmosphere. The lattice positions were discussed. It was found that when Ga3+ entered MAl2Si2O8 lattice and substituted Al3+, complete solid solutions formed. The lattice parameters (a, b, c) and unit cell volume of phosphors M 0.955Al2 –xGaxSi2O8: Eu2+ (M=Ca, Sr, Ba, x = 0~1.0) increased linearly, the lattice parameters (α, β,γ) of Ca0.955Al2–xGaxSi2O8∶Eu2+(CAS) decreased linearly and the lattice parameter β of Sr0.955Al2–xGaxSi2O8∶Eu2+(SAS) and Ba0.955Al2–xGaxSi2O8∶Eu2+(BAS) increased linearly as Ga3+ content increased.

Lattice Parameters of Gd-Doped Ceria Electrolytes

2005 ◽  
Vol 494 ◽  
pp. 175-180 ◽  
Author(s):  
B. Matović ◽  
Snezana Bošković ◽  
Ljiljana Živković ◽  
M.D. Vlajić ◽  
Vladimir D. Krstić
Keyword(s):  
Solid Solutions ◽  
Lattice Parameter ◽  
Lattice Parameters ◽  
Doped Ceria ◽  
Ceria Solid Solutions ◽  
Fluorite Type ◽  
Parameter Versus ◽  
Average Size ◽  
20 Nm ◽  
Type Crystal

This paper deals with Gd-doped ceria solid solutions: Ce1−XGdXO2−d with "x" ranging from 0 to 0.2. Four different powders were synthesized by modified glycine nitrate procedure with very precise stoichiometry according to tailored composition. The method was modified by decreasing glycine/nitrate ratio to 0.5. All obtained solid solutions exhibit a fluorite-type crystal structure with composition dependent lattice parameters. The variation of the lattice parameter was studied and correlated with the equation describing the ion-packing model. It has been found that the change of lattice parameter versus Gd concentration obeys Vegard's rule very well. Results also show that all powders are nanometric in size. The average size of Ce1−XGdXO2−d particles is about 20 nm.

Solid solubility and transport properties of Ce1−xNdxO2−δ nanocrystalline solid solutions by a sol-gel route

2001 ◽  
Vol 16 (11) ◽  
pp. 3207-3213 ◽  
Author(s):  
Liping Li ◽  
Xiaomin Lin ◽  
Guangshe Li ◽  
Hiroshi Inomata
Keyword(s):  
Activation Energy ◽  
Solid Solutions ◽  
Solid Solubility ◽  
Oxygen Vacancies ◽  
Sol Gel ◽  
Broad Band ◽  
Sample Surface ◽  
Fluorite Structure ◽  
Lattice Parameter ◽  
Dopant Content

Ce1−xNdxO2−δ (x = 0.05 to 0.55) nanocrystalline solid solutions were prepared by a sol-gel route. X-ray diffraction analysis showed that Ce1−xNdxO2−δ crystallized in a cubic fluorite structure. The lattice parameter for the solid solutions increased linearly with the dopant content. The solid solubility of Nd3+ in ceria lattice was determined to be about x = 0.40 in terms of the nearly constant lattice parameters at a dopant level larger than x = 0.40. First-order Raman spectra for Ce1−xNdxO2−δ at a lower dopant content exhibited one band associated with the F2g mode. At higher dopant contents, F2g mode became broadened and asymmetric, and a new broad band appeared at the higher frequency side of the F2g mode. This new band was assigned to the oxygen vacancies. The electron paramagnetic resonance spectrum for x = 0.05 showed the presence of O2− adsorbed on sample surface at g = 2.02 and 2.00 and of Ce3+ with a lower symmetry at g = 1.97 and 1.94. Further increasing dopant content led to the disappearance of the signals for O2−. Impedance spectra showed the bulk and grain boundary conduction in the solid solutions. The bulk conduction exhibited a conductivity maximum and an activation energy minimum with increasing dopant content. Ce0.80Nd0.20O2−δ was determined to give promising conduction properties such as a relatively high conductivity of σ700 °C = 2.44 × 10−2 S cm−1 and moderate activation energy of Ea = 0.802 eV. The variations of conductivity and activation energy were explained in terms of relative content of oxygen vacancies Vö and defect associations {CeCe ′Vö}/{NdCe ′Vö}.

Hydrothermal Synthesis and Characterization of Nb5+-Doped SrTiO3 Powders

2013 ◽  
Vol 821-822 ◽  
pp. 913-916 ◽  
Author(s):  
Fan Zhang ◽  
Li Zhi Shi ◽  
Yang Liu ◽  
Rui Liang Su ◽  
Zhan Jie Wang
Keyword(s):  
Hydrothermal Synthesis ◽  
Perovskite Structure ◽  
Dopant Concentration ◽  
Hydrothermal Reaction ◽  
Lattice Parameter ◽  
Lattice Parameters ◽  
Partial Substitution ◽  
Synthesis And Characterization ◽  
Diffraction Peaks

Nb5+-doped SrTiO3(STO) particles were synthesized by a simple hydrothermal reaction at 150 °C for 4h. It was found that the main diffraction peaks of Nb5+-doped STO samples with different dosage of dopants shifted gradually to low angles, indicating the little lattice parameter expansions which result from the partial substitution of Ti4+(0.061 nm) by Nb5+(0.064 nm) in perovskite structure. From the lattice parameters, the max Nb5+dopant concentration is about 2 mol%, and the particles obtained were 200 nm-sized and monodispersed.

Synthesis and Characterization of Manganese Substituted Cerium Oxide Nanoparticles by Microwave Refluxing Method

2015 ◽  
Vol 830-831 ◽  
pp. 608-611 ◽  
Author(s):  
Santhosh Kumar Alla ◽  
Vishal Yeddu ◽  
Eswara Vara Prasad Rao ◽  
Rajiv Kumar Mandal ◽  
Nand Kishore Prasad
Keyword(s):  
Cerium Oxide ◽  
Lattice Strain ◽  
Lattice Parameter ◽  
Synthesis And Characterization ◽  
Cerium Oxide Nanoparticles ◽  
Oxide Nanoparticles ◽  
Tem Analysis ◽  
Main Band ◽  
Mn Content

Nanocrystalline MnxCe1-xO2 (0 ≤ x ≤ 0.5) powders have been synthesized by microwave refluxing method. XRD, Raman spectroscopy and TEM analysis confirm the substitution of Mn in cerium oxide to a large extent. With increased Mn content, the crystallite size and lattice parameter found to be decreased. In addition, shifting of Raman main band towards lower frequency side was also observed with increased Mn. This could be attributed to the distortion of lattice of CeO2 due to the lattice strain induced by substitution of Mn.

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