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.

Cr-Doping-Induced Ferromagnetism in CeO2-δ Nanopowders

2014 ◽  
Vol 975 ◽  
pp. 42-49
Author(s):  
Nilson S. Ferreira ◽  
Marcelo Andrade Macedo
Keyword(s):  
Raman Spectroscopy ◽  
Saturation Magnetization ◽  
Calcination Temperature ◽  
Room Temperature ◽  
Magnetic Measurements ◽  
Room Temperature Ferromagnetism ◽  
Sol Gel ◽  
Fluorite Structure ◽  
Sol Gel Process ◽  
Cr Doping

The room-temperature ferromagnetism of Cr-doped cerium oxide (Ce0.96Cr0.04O2δ) nanopowders synthesized using a sol-gel process is reported in this paper. XRD and Raman spectroscopy confirm that the Cr atoms successfully displaced some of the Ce atoms in the CeO2lattice without forming any impure phases. The results also confirmed that all calcined samples exhibited a single-phase fluorite structure. The crystallite size (as confirmed by XRD) and the particle size (as confirmed by Raman spectroscopy) increased as the calcination temperature increased. Magnetic measurements indicated that the room-temperature ferromagnetism of the sample was sensitive to the calcination temperature. When the calcination temperature increased, the saturation magnetization decreased while the coercivity increased, which corresponds to less dense and larger particles. The calcined sample at 400°C exhibited superior magnetic properties with the highest saturation magnetization (Ms) of 2.5 × 10-2emu/g (Hc~ 1.27 kOe). The results of the Raman and X-ray photoelectron spectroscopies suggest that the nature of the observed room temperature ferromagnetism in the samples are likely a result of the oxygen vacancies induced by Cr-doping in CeO2.

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}.

Ionic Conductivity of Gd- and Y-Doped Ceria-Zirconia Solid Solutions

2006 ◽  
Vol 61 (7) ◽  
pp. 916-922 ◽  
Author(s):  
Vera Rührup ◽  
Hans-Dieter Wiemhöfer
Keyword(s):  
Ionic Conductivity ◽  
Solid Solutions ◽  
Oxygen Vacancies ◽  
Fluorite Structure ◽  
Lattice Parameter ◽  
Total Conductivity ◽  
Doped Ceria ◽  
Deep Minimum ◽  
X Ray ◽  
Zirconia Content

The total conductivity of the solid solutions (Ce1−xZrx)0.8Gd0.2O1.9 and (Ce1−xZrx)0.8Y0.2O1.9 was measured in air as a function of temperature (T = 300 °C- 600 °C) and composition (x = 0.0 - 0.9). A deep minimum of the bulk ionic conductivity was found for equal fractions of ceria and zirconia. It indicates enhanced defect association and ordering of the oxygen vacancies around x = 0.5. X-ray analysis (Guinier technique) showed the diffraction pattern of the cubic fluorite structure for all investigated compositions 0 < x < 1. The lattice parameter decreased linearly with increasing zirconia content x.

scholarly journals Review of Oxygen Vacancies in CeO2-doped Solid Solutions as Characterized by Raman Spectroscopy

2012 ◽  
Vol 28 (05) ◽  
pp. 1012-1020 ◽  
Author(s):  
LI Lan ◽  
◽  
HU Geng-Shen ◽  
LU Ji-Qing ◽  
LUO Meng-Fei
Keyword(s):  
Raman Spectroscopy ◽  
Solid Solutions ◽  
Oxygen Vacancies

Significant room-temperature ferromagnetism in porous ZnO films: The role of oxygen vacancies

2015 ◽  
Vol 200 ◽  
pp. 22-27 ◽  
Author(s):  
Xue Hou ◽  
Huiyuan Liu ◽  
Huiyuan Sun ◽  
Lihu Liu ◽  
Xiaoxuan Jia
Keyword(s):  
Room Temperature ◽  
Oxygen Vacancies ◽  
Room Temperature Ferromagnetism ◽  
Zno Films

Room-temperature ferromagnetism in polycrystalline Zn1–xFexO (0≤x≤0.075) solid solutions synthesized by the precursor method

2015 ◽  
Vol 162 ◽  
pp. 1-5 ◽  
Author(s):  
V.N. Krasilnikov ◽  
T.V. Dyachkova ◽  
О.I. Gyrdasova ◽  
А.P. Tyutyunnik ◽  
V.V. Marchenkov ◽  
...  
Keyword(s):  
Solid Solutions ◽  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Precursor Method

Structural and Ferromagnetic Properties of Ho-Doped BiFeO3 Films

2017 ◽  
Vol 727 ◽  
pp. 996-1000 ◽  
Author(s):  
Ning An ◽  
Hai Tao Zhang ◽  
Cheng Zhi Liu ◽  
Cun Bo Fan ◽  
Xue Dong ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Raman Spectroscopy ◽  
Room Temperature ◽  
Oxygen Vacancies ◽  
Sol Gel ◽  
Wave Number ◽  
Ferromagnetic Property ◽  
Peak Intensity ◽  
Structure Morphology ◽  
Xrd Patterns

In order to improve the structural and ferromagnetic property of BiFeO3, the effects of Ho3+ doping is systematically investigated. Pure BiFeO3 and Ho-doped BiFeO3 thin films are fabricated by sol-gel method, and the phase structure, morphology, crystalline structure, ferromagnetic are characterized by XRD, SEM, Raman spectra and VSM, respectively. The XRD patterns of the samples indicate that all the compounds crystallize in rhombohedral distorted perovskite structure with space group R3c and the Ho substitution can suppress the intrinsic formation of the miscellaneous phase. The SEM proves that along with the increasing of Ho concentration, the surface roughness of BiFeO3 is decreased due to the reduction of defects in the preparation. From the Raman spectroscopy, it is found that the peak intensity of 8 modes in Bi1-xHoxFeO3 are increased and the modes shift to higher wave number. Besides, the VSM results show that the ferromagnetic of the samples is enhanced with increasing of Ho concentration. When x=0.1, Ms is improved to be 4.8emu/g. The results can prove that the Ho3+ doping can reduce the volatilization of Bi3+, decrease the concentration of oxygen vacancies and improve the room-temperature ferromagnetic of BiFeO3.

Room-Temperature Ferromagnetism in Co-Doped SrTiO3 Nanofibres

2012 ◽  
Vol 512-515 ◽  
pp. 1438-1441
Author(s):  
Wei Zhang ◽  
He Ping Li ◽  
Wei Pan
Keyword(s):  
Room Temperature ◽  
Oxygen Vacancies ◽  
Room Temperature Ferromagnetism ◽  
Sol Gel ◽  
Magnetic Ordering ◽  
Second Phase ◽  
Co Doped

In this article, Co-doped SrTiO3 nanofibres have been prepared by electrospinning from a sol-gel precursor and the following calcination at 923K. XRD results confirmed that no second phase was formed, and Co ions successfully occupied the Ti sites. By annealing in hydrogen, oxygen vacancies and (Co-H-Co) were formed, which both contributed to the magnetic ordering in SrTi1-xCoxO3 nanofibres are at 300K.

Controlled Synthesis of Novel Popcorn-Like CeO2 Nanostructures and their Magnetic Properties

2017 ◽  
Vol 49 ◽  
pp. 27-33 ◽  
Author(s):  
Xiao Fei Niu ◽  
Fu Rong Tu
Keyword(s):  
Magnetic Properties ◽  
Raman Scattering ◽  
Room Temperature ◽  
Oxygen Vacancies ◽  
Magnetic Measurement ◽  
Fluorite Structure ◽  
Controlled Synthesis

The monodisperse popcorn-like CeO2 nanostructures with crude surface covered by wrinkles completely and a diameter of 150-300 nm have been successfully synthesized by a facile hydrothermal technology. XRD, SEM, XPS, Raman scattering and M-H curve were employed to characterize the samples. The results showed that the popcorn-like CeO2 nanostructures have a cubic fluorite structure and there are Ce3+ ions and oxygen vacancies existing in their surface. The magnetic measurement indicated that the popcorn-like CeO2 nanostructures possess excellent ferromagnetism at room temperature, which can be attributed to the influences of the morphology of the particles, Ce3+ ions and oxygen vacancies.

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