Oxygen transport studies in nanocrystalline ceria films

2005 ◽  
Vol 20 (5) ◽  
pp. 1295-1299 ◽  
Author(s):  
Laxmikant Saraf ◽  
C.M. Wang ◽  
V. Shutthanandan ◽  
Y. Zhang ◽  
Olga Marina ◽  
...  
Keyword(s):  
Grain Size ◽  
Ionic Conductivity ◽  
Oxygen Uptake ◽  
Defect Density ◽  
Sol Gel ◽  
Boundary Surface ◽  
Nuclear Reaction Analysis ◽  
Intermediate Temperature Range ◽  
Nanocrystalline Ceria ◽  
Impedance Technique

Oxygen uptake and conductivity were measured by nuclear-reaction analysis and alternating current impedance technique at the intermediate temperature range on sol-gel grown nanocrystalline ceria films with average grain-sizes 7 nm and 38 nm synthesized at 723 and 1173 K, respectively. Higher oxygen uptake and lower ionic conductivity were observed in ceria films with ∼7-nm grain size. High permeation-assisted oxygen diffusion in nanocrystallites combined with oxygen trapping in the disordered region contributed to higher oxygen uptake. However, the lower ionic conductivity in the film resulted from the absence of long-range lattice ordering and inactive grain-boundary/surface oxygen vacancy sites due to oxygenation. The relationship between oxygen uptake and conductivity in ceria is discussed in details by considering grain-size dependent defect density, related surface area, and enhanced oxygen mobility.

Oxygen Diffusivity and Defect Transport in Pure and Yb Doped Nano-crystalline Ceria

2003 ◽  
Vol 788 ◽  
Author(s):  
Laxmikant Saraf ◽  
V. Shutthanandan ◽  
S. Thevuthasan ◽  
C. M. Wang ◽  
K. T. Koch ◽  
...  
Keyword(s):  
Grain Size ◽  
Electrical Transport ◽  
Oxygen Diffusion ◽  
Defect Density ◽  
Sol Gel ◽  
Ionic Transport ◽  
Nuclear Reaction Analysis ◽  
Electrical Transport Properties ◽  
Nano Crystalline ◽  
Average Grain Size

ABSTRACTOxygen (18O) diffusivity in sol-gel synthesized nano-crystalline ceria films of average grain size of 3 nm and 7 nm, annealed at 300 °C and 450 °C for one hour respectively is examined by nuclear reaction analysis (NRA). Diffusivity and electrical transport properties measured by a. c. impedance spectroscopy were compared with microcrystalline ceria film of average grain size 38 nm annealed at 900 °C for one hour. Effect of enhanced oxygen diffusion along with reduced ionic transport in nano-crystalline ceria and reduced oxygen diffusion along with enhanced ionic transport in microcrystalline ceria are correlated to long range ordering, grain boundary scattering and defect density. Enhancement in the conductivity with reduction in activation energy from 1 eV to 0.5 eV in the case 4 atom% ytterbium (Yb) doped ceria compared to pure ceria is a result of increased oxygen vacancies taking part in the defect transport.

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.

The crystallization of thin-film ceramics

1992 ◽  
Vol 50 (1) ◽  
pp. 338-339
Author(s):  
J.M. Schwartz ◽  
L.F. Francis ◽  
L.D. Schmidt ◽  
P.S. Schabes-Retchkiman
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Sol Gel ◽  
Processing Route ◽  
Small Areas ◽  
Ceramic Thin Films ◽  
Complex Shapes ◽  
Sol Gel Process ◽  
Ceramic Precursors ◽  
Crystalline Ceramic

Ceramic thin films and coatings are of interest for electrical, optical, magnetic and thermal barrier applications. Critical for improved properties in thin films is the development of specific microstructures during processing. To this end, the sol-gel method is advantageous as a versatile processing route. The sol-gel process involves depositing a solution containing metalorganic or colloidal ceramic precursors onto a substrate and heating the deposited layer to form a crystalline or non-crystalline ceramic coating. This route has several advantages, including the ability to create tailored microstructures and properties, to coat large or small areas, simple or complex shapes, and to more easily prepare multicomponent ceramics. Sol-gel derived coatings are amorphous in the as-deposited state and develop their crystalline structure and microstructure during heat-treatment. We are particularly interested in studying the amorphous to crystalline transformation, because many key features of the microstructure such as grain size and grain size distribution may be linked to this transformation.

Characterization of New Ionically Conducting Peo-Based Networks by Diffusion, Elasticity Modulus and Ionic Conductivity Measurements

1992 ◽  
Vol 293 ◽  
Author(s):  
Herve Cheradame ◽  
F. Desbat ◽  
P. Mercier-Niddam ◽  
S. Boileau
Keyword(s):  
Diffusion Coefficient ◽  
Ionic Conductivity ◽  
Elasticity Modulus ◽  
Sol Gel ◽  
Cation Transport ◽  
Lithium Cation ◽  
Conductivity Measurements ◽  
Conducting Materials ◽  
Diffusion Studies

AbstractIonically conducting materials containing PEO were prepared from telechelic di(methyl-diethoxy-silane) PEO, synthesized by the hydrosilylation of telechelic diallyl-PEO with methyldiethoxysilane. The network is obtained by the usual sol-gel chemistry. Then, it is filled with LiClO4 by diffusion of the salt and further drying. A comparison is made with the same kind of materials crosslinked using urethane chemistry. Diffusion studies show that the diffusion coefficient of solvent is similar for both types of materials, whilst the ionic conductivity is higher for the networks crosslinked with siloxane bonds. An experiment of diffusion of LiClO4 without solvent showed that this salt has a diffusion coefficient of the order of 2.10-8 cm2.sec-1 at 34°C. The conductivity calculated from this determination is compatible with the mechanism of lithium cation transport by the diffusion of salt molecules. Elasticity modulus measurements show that the salt aggregates are essentially located within the crosslinks at low concentration, but also in the PEO chains for salt concentrations higher than 1 mol/l.

scholarly journals Fabrication and Analysis of Near-Field Electrospun PVDF Fibers with Sol-Gel Coating for Lithium-Ion Battery Separator

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 186
Author(s):  
Mark D. Francisco ◽  
Cheng-Tang Pan ◽  
Bo-Hao Liao ◽  
Mao-Sung Wu ◽  
Ru-Yuan Yang ◽  
...  
Keyword(s):  
Ionic Conductivity ◽  
Specific Capacitance ◽  
Near Field ◽  
Sol Gel ◽  
Lithium Ion ◽  
Nonwoven Fabric ◽  
Electrospun Fibers ◽  
Gel Method ◽  
Sol Gel Method ◽  
Microtensile Testing

Environmental and economic concerns are driving the demand for electric vehicles. However, their development for mass transportation hinges largely on improvements in the separators in lithium-ion batteries (LIBs), the preferred energy source. In this study, innovative separators for LIBs were fabricated by near-field electrospinning (NFES) and the sol-gel method. Using NFES, poly (vinylidene fluoride) (PVDF) fibers were fabricated. Then, PVDF membranes with pores of 220 nm and 450 nm were sandwiched between a monolayer and bilayer of the electrospun fibers. Nanoceramic material with organic resin, formed by the sol-gel method, was coated onto A4 paper, rice paper, nonwoven fabric, and carbon synthetic fabric. Properties of these separators were compared with those of a commercial polypropylene (PP) separator using a scanning electron microscope (SEM), microtensile testing, differential scanning calorimetry (DSC), ion-conductivity measurement, cyclic voltammetry (CV), and charge-discharge cycling. The results indicate that the 220 nm PVDF membrane sandwiched between a bilayer of electrospun fibers had excellent ionic conductivity (~0.57 mS/cm), a porosity of ~70%, an endothermic peak of ~175 °C, better specific capacitance (~356 mAh/g), a higher melting temperature (~160 °C), and a stable cycle performance. The sol-gel coated nonwoven fabric had ionic conductivity, porosity, and specific capacitance of ~0.96 mS/cm., ~64%, and ~220 mAh/g, respectively, and excellent thermal stability despite having a lower specific capacitance (65% of PP separator) and no peak below 270 °C. The present study provides a significant step toward the innovation of materials and processes for fabricating LIB separators.

scholarly journals Upscaling of LATP synthesis: Stoichiometric screening of phase purity and microstructure to ionic conductivity maps

Ionics ◽  
2021 ◽  
Vol 27 (5) ◽  
pp. 2017-2025
Author(s):  
Nikolas Schiffmann ◽  
Ethel C. Bucharsky ◽  
Karl G. Schell ◽  
Charlotte A. Fritsch ◽  
Michael Knapp ◽  
...  
Keyword(s):  
Ionic Conductivity ◽  
Sol Gel ◽  
Ion Conductivity ◽  
Process Window ◽  
Lithium Aluminum ◽  
Potential Candidate ◽  
Secondary Phases ◽  
X Ray Diffraction ◽  
Battery Cell ◽  
Li Ion

AbstractLithium aluminum titanium phosphate (LATP) is known to have a high Li-ion conductivity and is therefore a potential candidate as a solid electrolyte. Via sol-gel route, it is already possible to prepare the material at laboratory scale in high purity and with a maximum Li-ion conductivity in the order of 1·10−3 s/cm at room temperature. However, for potential use in a commercial, battery-cell upscaling of the synthesis is required. As a first step towards this goal, we investigated whether the sol-gel route is tolerant against possible deviations in the concentration of the precursors. In order to establish a possible process window for sintering, the temperature interval from 800 °C to 1100 °C and holding times of 10 to 480 min were evaluated. The resulting phase compositions and crystal structures were examined by X-ray diffraction. Impedance spectroscopy was performed to determine the electrical properties. The microstructure of sintered pellets was analyzed by scanning electron microscopy and correlated to both density and ionic conductivity. It is shown that the initial concentration of the precursors strongly influences the formation of secondary phases like AlPO4 and LiTiOPO4, which in turn have an influence on ionic conductivity, densification behavior, and microstructure evolution.

Study on the Grain Size of Vanadium Dioxide Thin Films using Sol-gel Spin Coating Method

2018 ◽  
Author(s):  
Ibrahim Mohd Yazid ◽  
Muhammad Hazim Raselan ◽  
Shafinaz Sobihana Shariffudin ◽  
Puteri Sarah Mohamad Saad ◽  
Sukreen Hana ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Vanadium Dioxide ◽  
Spin Coating ◽  
Sol Gel ◽  
Spin Coating Method ◽  
Coating Method ◽  
Vanadium Dioxide Thin Films

LiNiO2 Thin Films Fabricated by Diffusion of Li on Ni Tapes

2007 ◽  
Vol 336-338 ◽  
pp. 505-508
Author(s):  
Cheol Jin Kim ◽  
In Sup Ahn ◽  
Kwon Koo Cho ◽  
Sung Gap Lee ◽  
Jun Ki Chung
Keyword(s):  
Thin Films ◽  
Heat Treatment ◽  
Grain Size ◽  
Sol Gel ◽  
Surface Oxidation ◽  
Cold Isostatic Pressing ◽  
Tube Furnace ◽  
Treatment Conditions ◽  
Average Grain Size ◽  
Cold Rolling And Annealing

LiNiO2 thin films for the application of cathode of the rechargeable battery were fabricated by Li ion diffusion on the surface oxidized NiO layer. Bi-axially textured Ni-tapes with 50 ~ 80 μm thickness were fabricated using cold rolling and annealing of Ni-rod prepared by cold isostatic pressing of Ni powder. Surface oxidation of Ni-tapes were conducted using tube furnace or line-focused infrared heater at 700 °C for 150 sec in flowing oxygen atmosphere, resulted in NiO layer with thickness of 400 and 800 μm, respectively. After Li was deposited on the NiO layer by thermal evaporation, LiNiO2 was formed by Li diffusion through the NiO layer during subsequent heat treatment using IR heater with various heat treatment conditions. IR-heating resulted in the smoother surface and finer grain size of NiO and LiNiO2 layer compared to the tube-furnace heating. The average grain size of LiNiO2 layer was 0.5~1 μm, which is much smaller than that of sol-gel processed LiNiO2. The reacted LiNiO2 region showed homogeneous composition throughout the thickness and did not show any noticeable defects frequently found in the solid state reacted LiNiO2, but crack and delamination between the reacted LiNiO2 and Ni occurred as the reaction time increased above 4hrs.

Microwave Absorbing Ferrite Thin Films for Microwave Heating of Microstructured Reactors

2009 ◽  
Vol 1222 ◽  
Author(s):  
Pengzhao Gao ◽  
Evgeny V. Rebrov ◽  
Jaap C. Schouten ◽  
Richard Kleismit ◽  
John Cetnar ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Microwave Heating ◽  
Near Field ◽  
Coplanar Waveguide ◽  
Sol Gel ◽  
Microwave Cavity ◽  
Silicon Substrates ◽  
Microwave Microscopy ◽  
Zn Ferrite

AbstractNanocrystalline Ni0.5Zn0.5Fe2O4 thin films have been synthesized with various grain sizes by sol–gel method on polycrystalline silicon substrates. The morphology and microwave absorption properties of the films calcined in the 673–1073 K range were studied by using XRD, AFM, near–field evanescent microwave microscopy, coplanar waveguide and direct microwave heating measurements. All films were uniform without microcracks. The increase of the calcination temperature from 873 to 1073 K and time from 1 to 3h resulted in an increase of the grain size from 12 to 27 nm. The complex permittivity of the Ni-Zn ferrite films was measured in the frequency range of 2–15 GHz. The heating behavior was studied in a multimode microwave cavity at 2.4 GHz. The highest microwave heating rate in the temperature range of 315–355 K was observed in the film close to the critical grain size of 21 nm in diameter marked by the transition from single– to multi–domain structure of nanocrystals in Ni0.5Zn0.5Fe2O4 film and by a maximum in its coercivity.

Sintering behavior and ionic conductivity of Li1.5Al0.5Ti1.5(PO4)3 synthesized with different precursors

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Bambar Davaasuren ◽  
Qianli Ma ◽  
Alexandra von der Heiden ◽  
Frank Tietz
Keyword(s):  
Grain Size ◽  
Solid State ◽  
Ionic Conductivity ◽  
Solid State Reaction ◽  
Sintering Temperature ◽  
Sintering Behavior ◽  
Homogeneous Microstructure ◽  
Micro Cracks ◽  
Primary Particles ◽  
Total Ionic Conductivity

Abstract Li1.5Al0.5Ti1.5(PO4)3 (LATP) powders were prepared from different NO x -free precursors using an aqueous-based solution-assisted solid-state reaction (SA-SSR). The sintering behavior, phase formation, microstructure and ionic conductivity of the powders were explored as a function of sintering temperature. The powders showed a relatively narrow temperature windows in which shrinkage occurred. Relative densities of 95% were reached upon heating between 900 and 960 °C. Depending on the morphological features of the primary particles, either homogeneous and intact microstructures with fine grains of about <2 µm in size or a broad grain size distribution, micro-cracks and grain cleavages were obtained, indicating the instability of the microstructure. Consequently, the ceramics with a homogeneous microstructure possessed a maximum total ionic conductivity of 0.67 mS cm−1, whereas other ceramics reached only 0.58 mS cm−1 and 0.21 mS cm−1.

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