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.

Effect of Sonochemical, Regenerative Sol Gel and Microwave Assisted Synthesis Techniques on the Formation of Dense Electrolytes and Porus Electrodes for All Perovskite IT-SOFCs

2006 ◽  
Author(s):  
Hrudananda Jena ◽  
B. Rambabu
Keyword(s):  
Grain Size ◽  
Electrical Transport ◽  
Microwave Sintering ◽  
Sol Gel ◽  
Microwave Assisted Synthesis ◽  
Electrical Transport Properties ◽  
Chemical Methods ◽  
Nano Crystalline ◽  
Average Grain Size ◽  
Wet Chemical

The influence of preparation techniques on the microstructure, grain-size and consequently on the electrical transport properties of the ABO3 structured materials used as electrode and electrolytes in all perovskite IT-SOFC were investigated. Nano-crystalline powders of La1-xMxGa1-yNyO3±δ (M = Sr,; x = −0.10 to 0.15; N = Mg; y = −0.10 to 0.15) (LSGM) as electrolyte, porous La0.8Sr0.2Co0.8Fe0.2O3±δ (LSCF) or LaNi1-xFexO3±δ (x = 0–0.5) (LNF) as cathode, La0.8Sr0.2Cr0.7Mn0.3O3±δ (LSCM) as anode and LaCrO3 or substituted LaCrO 3 as interconnect were synthesized by various wet chemical methods. The wet chemical methods like metal-carboxylate gel decomposition, hydroxide co-precipitation, sonochemical and regenerative sol-gel process followed by microwave sintering of the powders have been used. Microwave sintering parameters were optimized by varying sintering time, and temperature to achieve higher density of LSGM pellets. The phase pure systems were obtained at sintering duration of 30 min at 1200 °C. The XRD, HR-TEM, and SEM measurements revealed the average grain size of these perovskites was ∼ 22 nm range. The electrical conductivities of the compositions were measured by ac (5Hz–13MHz) and dc techniques. The conductivity of the sintered pellets was found to be ∼0.01–0.21 S/cm at 550–1000°C range for electrolyte and 1.5–100 S/cm at 25–1000°C for electrodes respectively. The effect of sonochemical, and regenerative sol-gel methods in processing large quantities of nano-crystalline perovskites with multi-element substitutions at A- and B-sites to achieve physico-chemical compatibility for fabricating zero emission all perovskite IT-SOFCs are reported in this paper.

Effect of Sintering on Structural and Transport Properties on Nanosized Pr0.85Na0.15MnO3

2015 ◽  
Vol 1107 ◽  
pp. 272-277 ◽  
Author(s):  
Siau Wei Ng ◽  
Kean Pah Lim ◽  
S.A. Halim ◽  
Hassan Jumiah ◽  
Albert H.M. Gan ◽  
...  
Keyword(s):  
Grain Size ◽  
Transport Properties ◽  
Electrical Transport ◽  
Boundary Effect ◽  
Sol Gel ◽  
Magnetic Layer ◽  
Electrical Transport Properties ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Semiconductor Behavior

We have investigated the structural, microstructure and electrical transport properties of nanosized Pr0.85Na0.15MnO3 (PNMO) synthesized by sol-gel technique and sinter from 600°C to 1000°C. The grain size increases from 67 nm (S600) up to 284 nm (S1000) due to the grain growth during heat treatment. XRD showed that single phase orthorhombic crystal structure of PNMO is fully forms started at 600°C. The resistivity decreased with the increased of grain size and crystallite size due to the reduction of grain boundary effect (dead magnetic layer) which improved their grain conductivity.All samples showed semiconductor behavior where their metal insulator transition temperatures (TMIT) were estimated to be lower than 80K.

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.

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.

scholarly journals The Influence of Annealing Temperature on the Structure and Magnetic Properties of Nanocrystalline BiFeO3 Prepared by Sol–Gel Method

2021 ◽  
Author(s):  
T. Pikula ◽  
T. Szumiata ◽  
K. Siedliska ◽  
V. I. Mitsiuk ◽  
R. Panek ◽  
...  
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Annealing Temperature ◽  
Sol Gel ◽  
Weak Ferromagnetism ◽  
X Ray Diffraction ◽  
Gel Method ◽  
Sol Gel Method ◽  
Average Grain Size ◽  
Spin Cycloid

AbstractIn this work, BiFeO3 powders were synthesized by a sol–gel method. The influence of annealing temperature on the structure and magnetic properties of the samples has been discussed. X-ray diffraction studies showed that the purest phase was formed in the temperature range of 400 °C to 550 °C and the samples annealed at a temperature below 550 °C were of nanocrystalline character. Mössbauer spectroscopy and magnetization measurements were used as complementary methods to investigate the magnetic state of the samples. In particular, the appearance of weak ferromagnetic properties, significant growth of magnetization, and spin-glass-like behavior were observed along with the drop of average grain size. Mössbauer spectra were fitted by the model assuming cycloidal modulation of spins arrangement and properties of the spin cycloid were determined and analyzed. Most importantly, it was proved that the spin cycloid does not disappear even in the case of the samples with a particle size well below the cycloid modulation period λ = 62 nm. Furthermore, the cycloid becomes more anharmonic as the grain size decreases. The possible origination of weak ferromagnetism of the nanocrystalline samples has also been discussed.

scholarly journals Effect of Solution Conditions on the Properties of Sol–Gel Derived Potassium Sodium Niobate Thin Films on Platinized Sapphire Substrates

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1600 ◽  
Author(s):  
Alexander Tkach ◽  
André Santos ◽  
Sebastian Zlotnik ◽  
Ricardo Serrazina ◽  
Olena Okhay ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Low Cost ◽  
Sol Gel ◽  
Precursor Solution ◽  
Dissipation Factor ◽  
Solution Concentration ◽  
Potassium Sodium Niobate ◽  
Sapphire Substrates ◽  
Average Grain Size

If piezoelectric micro-devices based on K0.5Na0.5NbO3 (KNN) thin films are to achieve commercialization, it is critical to optimize the films’ performance using low-cost scalable processing conditions. Here, sol–gel derived KNN thin films are deposited using 0.2 and 0.4 M precursor solutions with 5% solely potassium excess and 20% alkali (both potassium and sodium) excess on platinized sapphire substrates with reduced thermal expansion mismatch in relation to KNN. Being then rapid thermal annealed at 750 °C for 5 min, the films revealed an identical thickness of ~340 nm but different properties. An average grain size of ~100 nm and nearly stoichiometric KNN films are obtained when using 5% potassium excess solution, while 20% alkali excess solutions give the grain size of 500–600 nm and (Na + K)/Nb ratio of 1.07–1.08 in the prepared films. Moreover, the 5% potassium excess solution films have a perovskite structure without clear preferential orientation, whereas a (100) texture appears for 20% alkali excess solutions, being particularly strong for the 0.4 M solution concentration. As a result of the grain size and (100) texturing competition, the highest room-temperature dielectric permittivity and lowest dissipation factor measured in the parallel-plate-capacitor geometry were obtained for KNN films using 0.2 M precursor solutions with 20% alkali excess. These films were also shown to possess more quadratic-like and less coercive local piezoelectric loops, compared to those from 5% potassium excess solution. Furthermore, KNN films with large (100)-textured grains prepared from 0.4 M precursor solution with 20% alkali excess were found to possess superior local piezoresponse attributed to multiscale domain microstructures.

Structural and Morphological Studies of Cadmium Sulfide Nanostructures

2013 ◽  
Vol 795 ◽  
pp. 228-232 ◽  
Author(s):  
Abdulwahab S.Z. Lahewil ◽  
Y. Al-Douri ◽  
U. Hashim ◽  
Naser Mahmoud Ahmed
Keyword(s):  
Grain Size ◽  
Cadmium Sulfide ◽  
Spin Coating ◽  
Sol Gel ◽  
Theoretical Data ◽  
Glass Substrates ◽  
Morphological Studies ◽  
Average Grain Size ◽  
Cds Nanostructures ◽  
Semiconductor Properties

Cadmium sulfide (CdS) nanostructures were prepared with different spin coating speed 1000 and 3000 rpm and molarities of Cd:S to be 1.2 to 0.01 mol/L using sol-gel spin coating technique. It is found that the average grain size of CdS nanostructures deposited on glass substrates at 1000 and 3000 rpm is 43 to 4 nm respectively. The effect of grain size on the semiconductor properties are in agreement with experimental and theoretical data.

scholarly journals Sol-Gel Processed Yttrium-Doped SnO2 Thin Film Transistors

Electronics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 254 ◽  
Author(s):  
Changmin Lee ◽  
Won-Yong Lee ◽  
Hyunjae Lee ◽  
Seunghyun Ha ◽  
Jin-Hyuk Bae ◽  
...  
Keyword(s):  
Thin Film ◽  
Oxygen Vacancy ◽  
Electrical Transport ◽  
Thin Film Transistors ◽  
Vacancy Concentration ◽  
Operation Mode ◽  
Sol Gel ◽  
Sno2 Thin Film ◽  
Oxygen Vacancy Concentration ◽  
Electrical Transport Properties

Y-doped SnO2 thin film transistors were successfully fabricated by means of sol-gel process. The effect of Y concentration on the structural, chemical, and electrical properties of sol-gel-processed SnO2 films was investigated via GIXRD, SPM, and XPS; the corresponding electrical transport properties of the film were also evaluated. The dopant, Y, can successfully control the free carrier concentration by suppressing the formation of oxygen vacancy inside SnO2 semiconductors due to its lower electronegativity and SEP. With an increase of Ywt%, it was observed that the crystallinity and oxygen vacancy concentration decreased, and the operation mode of SnO2 thin film transistor changed from accumulation (normally on) to enhancement mode (normally off) with a positive Vth shift.

The Effect of Sintering Temperature on the Crystal Structure and Luminescence Properties of Pr:LSO Polycrystalline Films

2016 ◽  
Vol 852 ◽  
pp. 1080-1086
Author(s):  
Xiao Xin Zhang ◽  
Jian Jun Xie ◽  
Ying Shi ◽  
Ling Cong Fan ◽  
De Bao Lin ◽  
...  
Keyword(s):  
Thin Film ◽  
Grain Size ◽  
Decay Time ◽  
Sintering Temperature ◽  
Coating Layer ◽  
Sol Gel ◽  
Characteristic Emission ◽  
Average Grain Size ◽  
Lutetium Oxyorthosilicate ◽  
Xrd Patterns

Lutetium oxyorthosilicate (Lu2SiO5, LSO) doped with Pr3+ was synthesized on cleaned silicon (111) substrates by sol-gel route with the spin-coating technique. XRD patterns indicated that the films were crystallized into A-type LSO phase at 1000 °C, followed by a phase transition to B-type LSO occurred at 1100 °C. SEM observations revealed that the surface of the films was smooth, homogeneous and crack-free. When the sintering temperature was 1000 °C, the average grain size of the crystal particles was 100-200 nm and the thickness of the thin film was about 380 nm when the coating layer number up to 10. While the sintering temperature was 1100 °C, the average grain size of the crystal particles was 200-300 nm and the thickness of the thin film was about 320 nm also 10 layers. PL spectra showed when under 1000 °C, the quenching concentration of Pr3+ was 0.3 mol%, the characteristic emission peaks was 289 nm and 340 nm and the dominant decay time was 4.64 ns; while under 1100 °C, the quenching concentration of Pr3+ was 0.4 mol%, the characteristic emission peaks was 280 nm and 320 nm and the dominant decay time was 2.61 ns.

Magnetic and electrical transport properties of Sr2Ti1−xCoxO4 ceramics by sol–gel

2017 ◽  
Vol 31 (17) ◽  
pp. 1750195
Author(s):  
Li Zhang ◽  
Yibao Li ◽  
Zhen Tang ◽  
Yan Deng ◽  
Hui Yuan ◽  
...  
Keyword(s):  
Transport Properties ◽  
Electrical Transport ◽  
Low Temperatures ◽  
Sol Gel ◽  
Variable Range Hopping ◽  
Electrical Transport Properties ◽  
Co Doping ◽  
Hopping Model ◽  
Variable Range Hopping Model ◽  
Co Doped

Microstructures, electrical transport and magnetic properties of Sr[Formula: see text]Ti[Formula: see text]Co[Formula: see text]O[Formula: see text] ceramics are investigated. With Co doping, the Sr[Formula: see text]Ti[Formula: see text]Co[Formula: see text]O[Formula: see text] ceramics remain tetragonal structure while the grain size is decreased with doping. Magnetic moment is enhanced with Co doping and ferromagnetism is observed at low temperatures for Co-doped Sr[Formula: see text]TiO[Formula: see text]. The Sr[Formula: see text]Ti[Formula: see text]Co[Formula: see text]O[Formula: see text] and Sr[Formula: see text]Ti[Formula: see text]Co[Formula: see text]O[Formula: see text] show semiconductor-like transport properties, which can be well fitted by Mott variable range hopping model. The results will provide an effective route to synthesize Sr[Formula: see text]Ti[Formula: see text]Co[Formula: see text]O[Formula: see text] ceramics as well as to investigate the physical properties.

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