Ionic conductivity in nanocrystalline Gd doped ceria

2008 ◽  
Vol 1122 ◽  
Author(s):  
Gianguido Baldinozzi ◽  
David Simeone ◽  
Dominique Gosset ◽  
Mickael Dollé ◽  
Georgette Petot-Ervas
Keyword(s):  
Grain Size ◽  
Ionic Conductivity ◽  
Sol Gel ◽  
Doped Ceria ◽  
Narrow Size Distribution ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes ◽  
The Impact

AbstractWe have synthesized Gd-doped ceria polycrystalline samples (5, 10, 15 %mol), having relative densities exceeding 95% and grain sizes between 30 and 160 nm after axial hot pressing (750 °C, 250 MPa). The samples were prepared by sintering nanopowders obtained by sol-gel chemistry methods having a very narrow size distribution centered at about 16 nm. SEM and X-ray diffraction were performed to characterize the sample microstructures and to assess their structures. We report ionic conductivity measurements using impedance spectroscopy. It is important to investigate the properties of these systems with sub-micrometric grains and as a function of their composition. Therefore, samples having micrometric and nanometric grain sizes (and different Gd content) were studied. Evidence of Gd segregation near the grain boundaries is given and the impact on the ionic conductivity, as a function of the grain size and Gd composition, is discussed and compared to microcrystalline samples.

A CRYSTAL STRUCTURE STUDY OF La1-xCaxMnO3 NANOPARTICLES

2004 ◽  
Vol 18 (12n13) ◽  
pp. 597-602 ◽  
Author(s):  
YINGWEN DUAN ◽  
JIANGONG LI
Keyword(s):  
Crystal Structure ◽  
Grain Size ◽  
Surface Effect ◽  
Sol Gel ◽  
Structure Study ◽  
X Ray Diffraction ◽  
Structure Transition ◽  
X Ray ◽  
Grain Sizes ◽  
Average Grain Size

Using a sol-gel method, La 1-x Ca x MnO 3(0≤x≤0.5) nanoparticles with nearly the same average grain size of about 21 nm and different Ca contents, La 0.8 Ca 0.2 MnO 3 nanoparticles with various average grain sizes were prepared. Crystal structure was investigated by X-ray diffraction. Increasing Ca content and decreasing grain size can lead to the average Mn–O bond lengths decrease and Mn–O–Mn bond angles increase. The crystal symmetry changes from orthorhombic to cubic as x≥0.3 for the La 1-x Ca x MnO 3(0≤x≤0.5) nanoparticles with nearly the same average grain size and D~16 nm for the La 0.8 Ca 0.2 MnO 3 nanoparticles with various grain sizes. Small-size effect and surface effect may be the reasons of the lattice distortion and structure transition.

scholarly journals High Pressure X-ray Diffraction as a Tool for Designing Doped Ceria Thin Films Electrolytes

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 724
Author(s):  
Sara Massardo ◽  
Alessandro Cingolani ◽  
Cristina Artini
Keyword(s):  
Thin Films ◽  
High Pressure ◽  
Rare Earth ◽  
Ionic Conductivity ◽  
Bulk Material ◽  
Threshold Temperature ◽  
Doped Ceria ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rare Earth Doped

Rare earth-doped ceria thin films are currently thoroughly studied to be used in miniaturized solid oxide cells, memristive devices and gas sensors. The employment in such different application fields derives from the most remarkable property of this material, namely ionic conductivity, occurring through the mobility of oxygen ions above a certain threshold temperature. This feature is in turn limited by the association of defects, which hinders the movement of ions through the lattice. In addition to these issues, ionic conductivity in thin films is dominated by the presence of the film/substrate interface, where a strain can arise as a consequence of lattice mismatch. A tensile strain, in particular, when not released through the occurrence of dislocations, enhances ionic conduction through the reduction of activation energy. Within this complex framework, high pressure X-ray diffraction investigations performed on the bulk material are of great help in estimating the bulk modulus of the material, and hence its compressibility, namely its tolerance toward the application of a compressive/tensile stress. In this review, an overview is given about the correlation between structure and transport properties in rare earth-doped ceria films, and the role of high pressure X-ray diffraction studies in the selection of the most proper compositions for the design of thin films.

Heterogeneity Effects in X-Ray Analysis*

1961 ◽  
Vol 5 ◽  
pp. 335-354 ◽  
Author(s):  
Fernand Claisse ◽  
Claude Samson
Keyword(s):  
Grain Size ◽  
Size Effect ◽  
Mathematical Treatment ◽  
Grain Size Effect ◽  
Light Elements ◽  
X Ray Diffraction ◽  
Limited Region ◽  
X Ray ◽  
Grain Sizes ◽  
Heterogeneity Effects

AbstractA fundamental quantitative treatment of the heterogeneity effects in X-ray fluorescence has been made. The theory predicts that the grain-size effect appears only in a limited region of grain sizes which depends on the wavelength of the primary radiation and the nature of the compounds in the mixture. With monochromatic radiation, the fluorescence intensity showed increase or decrease by a factor of a few units as grain size is decreased, A factor as large as 12, the theoretical value, has been observed in one particular experiment. Usually the grain-size effect can be eliminated by intensive grinding. For the light elements fine grinding is disastrous if long wavelengths are used. By an appropriate choice of the wavelength it is possible to eliminate the effect even without grinding. The mathematical treatment also predicts, but less rigorously, a grain-size effect in X-ray diffraction.The effect on the fluorescence intensities by changes in the chemical composition of the grains that contain the fluorescent element is predicted by the theory.These findings are discussed in relation to the analysis of elements when polychromatic beams are used.

Lithium chromium pyrophosphate as an insertion material for Li-ion batteries

2015 ◽  
Vol 71 (6) ◽  
pp. 661-667 ◽  
Author(s):  
Martin Reichardt ◽  
Sébastien Sallard ◽  
Petr Novák ◽  
Claire Villevieille
Keyword(s):  
Sol Gel ◽  
Insertion Reaction ◽  
Li Ion Batteries ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
Theoretical Limit ◽  
X Ray ◽  
Electrochemically Active ◽  
Carbon Coated ◽  
Li Ion

Lithium chromium pyrophosphate (LiCrP2O7) and carbon-coated LiCrP2O7 (LiCrP2O7/C) were synthesized by solid-state and sol–gel routes, respectively. The materials were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and conductivity measurements. LiCrP2O7 powder has a conductivity of ∼ 10−8 S cm−1, ∼ 104 times smaller than LiCrP2O7/C (∼ 10−4 S cm−1). LiCrP2O7/C is electrochemically active, mainly between 1.8 and 2.2 V versus Li+/Li (Cr3+/Cr2+ redox couple), whereas LiCrP2O7 has limited electrochemical activity. LiCrP2O7/C delivers a reversible specific charge up to ∼ 105 mAh g−1 after 100 cycles, close to the theoretical limit of 115 mAh g−1. Operando XRD experiments show slight peak shifts between 2.2 and 4.8 V versus Li+/Li, and a reversible amorphization between 1.8 and 2.2 V versus Li+/Li, suggesting an insertion reaction mechanism.

scholarly journals Impact of alumina particles on the morphology and mechanics of hybrid wood plastic composite materials

2019 ◽  
Vol 51 (1) ◽  
pp. 115-124 ◽  
Author(s):  
Srdjan Perisic ◽  
Marija Vuksanovic ◽  
Milos Petrovic ◽  
Andjela Radisavljevic ◽  
Aleksandar Grujic ◽  
...  
Keyword(s):  
Hybrid Composite ◽  
Moisture Absorption ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Pressing Method ◽  
X Ray ◽  
Plastic Composite ◽  
Alumina Particles ◽  
Gel Technique ◽  
The Impact

Hybrid composite panels of Wood-Plastic Composites (WPC) consisting of wood and poly (methyl methacrylate) (PMMA) were reinforced with alumina particles and made by ?hot pressing? method. Alumina-based particles were made by sol-gel technique. The particles were characterized by the X-ray diffraction (XRD). The resulting alumina particles were modified with (3mercaptopropyl) trimethoxysilane (MPTMS), in order to obtain better mechanical properties of the composite relative to the composite with unmodified alumina particles. The aim of this work was to study the influence of composite structure and the moisture absorption on bending and the impact properties of the hybrid composite. The bending and impact tests revealed that modulus of elasticity and absorbed energy of deformation increased with modification of alumina and slightly decrease after moisture absorption.

scholarly journals Enhancement of Photocatalytic Activity by Mg2+ Doped Ceria Quantum Dots

2017 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Quantum Dots ◽  
Photocatalytic Activity ◽  
Quantum Dot ◽  
Sol Gel ◽  
Lattice Parameter ◽  
Doped Ceria ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gel Technique ◽  
Cubic Structure

The pure and Mg2+ doped CeO2 quantum dot were synthesized by sol-gel technique. The prepared quantum dots were characterized using X-ray diffraction pattern (XRD), Scanning electron microscope (SEM-EDX). The XRD results show cubic structure of the CeO2 quantum dots. The crystalline size (D), microstrain (ε), dislocation density (δ) and lattice parameter (α) were calculated and analyzed. SEM-EDX analysis shows the morphology and the presence of elements. The photocatalytic activity of the synthesized quantum dot was evaluated based on the photodegradation of methylene blue (MB) by UV-Vis spectrometry.

scholarly journals Synthesis of ZnO-CdO Nanocomposites

2013 ◽  
Vol 1 (1) ◽  
pp. 11-14
Author(s):  
N. Sahu ◽  
◽  
R. K. Duchaniya ◽  
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Low Cost ◽  
Sol Gel ◽  
Particle Size Analysis ◽  
Synthesis Process ◽  
Size Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

The ZnO-CdO nanocomposite was prepared by sol-gel method by using their respective nitrates. It is a simple and low cost method to prepare nanocomposites. The drying temperature and drying period of prepared gel was varied during the synthesis process. The prepared samples were characterized by using scanning electron microscope (SEM), particle size analysis (PSA), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL) to get surface morphology, idea of getting particle of nanosized range so that further characterizations can be done, to study the optical property of synthesized nanocomposite and measure the band gap . The grain size determined by Scherrer’s formula was found to be between 30-50 nm.

Luminescence properties of R2MoO6:Eu3+ (R = Gd, Y, La) phosphors prepared by Pechini sol-gel process

2005 ◽  
Vol 20 (10) ◽  
pp. 2676-2681 ◽  
Author(s):  
Maolin Pang ◽  
Xiaoming Liu ◽  
Jun Lin
Keyword(s):  
Grain Size ◽  
Sol Gel ◽  
Luminescent Properties ◽  
Luminescence Properties ◽  
X Ray Diffraction ◽  
Powder Morphology ◽  
X Ray ◽  
Average Grain Size ◽  
Sem Study ◽  
Sol Gel Process

R2MoO6:Eu3+ (R = Gd, Y, La) phosphors were prepared by the Pechini sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), reflectance spectra, photoluminescence (PL) spectra, and lifetimes were used to characterize the resulting phosphors. The results of XRD indicate that all of the R1.96Eu0.04MoO6 (R = Gd, Y, La) phosphors crystallized completely at 800 °C. Y1.96Eu0.04MoO6 and Gd1.96Eu0.04MoO6 are of isomorphous monoclinic (α) structure, while La1.96Eu0.04MoO6 preferentially adopts the tetragonal (γ) form. FE-SEM study reveals that the samples mainly consist of aggregated particles with an average grain size ranging from 100 to 250 nm. The luminescent properties of R2MoO6:Eu3+ (R = Gd, Y, La) phosphors are largely dependent on their structure, grain size, and powder morphology. The isomorphous Y2MoO6:Eu3+ and Gd2MoO6:Eu3+ phosphors show very similar luminescence properties, which differ greatly from that of the La2MoO6:Eu3+ phosphor.

Dislocations in Submicron Grain Size and Nanocrystalline Copper

2000 ◽  
Vol 634 ◽  
Author(s):  
T. Ungár ◽  
G. Tichy ◽  
P. G. Sanders ◽  
J. R. Weertman
Keyword(s):  
Grain Size ◽  
Profile Analysis ◽  
Dislocation Model ◽  
X Ray Diffraction ◽  
Strain Anisotropy ◽  
Nanocrystalline Copper ◽  
X Ray ◽  
Gas Condensation ◽  
Grain Sizes ◽  
20 Nm

ABSTRACTUsing the dislocation model of strain anisotropy in X-ray diffraction peak profile analysis it is shown that in nanocrystalline copper produced by inert gas condensation dislocations are present, at least, down to average grain sizes of the order of 20 nm. Based on the analysis of the dislocation contrast factors it is suggested that with decreasing grain size the proportion of Lomer-Cottrell type dislocations increases.

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