Hydrothermal Synthesis and Properties of Ce1−xMxO2-δ(M = La, Bi, Sm, Pr, Tb) Solid Solutions

1998 ◽  
Vol 548 ◽  
Author(s):  
M. Greenblatt ◽  
P. Shuk ◽  
W. Huang ◽  
S. Dikmen ◽  
M. Croft
Keyword(s):  
Solid Solutions ◽  
Ultrafine Particles ◽  
Electronic Conductivity ◽  
Solubility Limit ◽  
Hydrothermal Conditions ◽  
Oxide Systems ◽  
Oxide Ion Conductivity ◽  
Maximum Conductivity ◽  
Crystallite Dimension ◽  
20 Nm

ABSTRACTA systematic study of hydrothermally prepared Ce1−x,MxO2−δ, (M= Sm, Bi, Pr, Tb; x= 0-0.30) solid solutions, promising materials for application in solid oxide fuel cells and oxygen membranes is presented. Ultrafine particles of uniform crystallite dimension, ∼ 20 nm can be formed in 30 min. under hydrothermal conditions (260°C, 10 MPa). The small particle size (20-50 nm) of the hydrothermally prepared materials allows sintering of the samples into highly dense ceramics at 900-1350°C, significantly lower temperatures than 1600-1650°C required for samples prepared by solid state techniques. The solubility limit of Bi2O3, in CeO2, was determined to be around 20 mol. %. The maximum conductivity, σ600°C ∼ 4.4 × 10−3 S/cm with Ea = 1.01 eV, and σ600°C = 5.7 × 10−3 S/cm with Ea ≈ 0.9 eV was found at x= 0.20 and x= 0.17 for Bi and Sm, respectively. In the Ce-Pr/Tb oxide systems, in addition to the high oxide ion conductivity, electronic conductivity occurs through the hopping of small polarons by a thermally activated mechanism (electron hopping from the Pr3+/Tb3+ to a neighboring Pr4+/Tb4+ ion).

scholarly journals Summertime observations of ultrafine particles and cloud condensation nuclei from the boundary layer to the free troposphere in the Arctic

2016 ◽  
Author(s):  
Julia Burkart ◽  
Megan D. Willis ◽  
Heiko Bozem ◽  
Jennie L. Thomas ◽  
Kathy Law ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ultrafine Particles ◽  
Cloud Condensation Nuclei ◽  
Particle Diameter ◽  
Open Ocean ◽  
The Arctic ◽  
Condensation Nuclei ◽  
Aerosol Composition ◽  
Low Level ◽  
20 Nm

Abstract. The Arctic is extremely sensitive to climate change. Shrinking sea ice extent increases the area covered by open ocean during Arctic summer, which impacts the surface albedo and aerosol and cloud properties among many things. In this context extensive aerosol measurements (aerosol composition, particle number and size, cloud condensation nuclei, and trace gases) were made during 11 flights of the NETCARE July, 2014 airborne campaign conducted from Resolute Bay, Nunavut (74N, 94W). Flights routinely included vertical profiles from about 60 to 3000 m a.g.l. as well as several low-level horizontal transects over open ocean, fast ice, melt ponds, and polynyas. Here we discuss the vertical distribution of ultrafine particles (UFP, particle diameter, dp: 5–20 nm), size distributions of larger particles (dp: 20 nm to 1 μm), and cloud condensation nuclei (CCN, supersaturation = 0.6 %) in relation to meteorological conditions and underlying surfaces. UFPs were observed predominantly within the boundary layer, where concentrations were often several hundreds to a few thousand particles per cubic centimeter. Occasionally, particle concentrations below 10 cm−3 were found. The highest UFP concentrations were observed above open ocean and at the top of low-level clouds, whereas numbers over ice-covered regions were substantially lower. Overall, UFP formation events were frequent in a clean boundary layer with a low condensation sink. In a few cases this ultrafine mode extended to sizes larger than 40 nm, suggesting that these UFP can grow into a size range where they can impact clouds and therefore climate.

scholarly journals Thermodynamic Analysis of the Formation of FCC and BCC Solid Solutions of Ti-Based Ternary Alloys by Mechanical Alloying

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 510 ◽  
Author(s):  
Claudio Aguilar ◽  
Carola Martinez ◽  
Karem Tello ◽  
Sergio Palma ◽  
Adeline Delonca ◽  
...  
Keyword(s):  
Free Energy ◽  
Mechanical Alloying ◽  
Gibbs Free Energy ◽  
Thermodynamic Analysis ◽  
Solid Solutions ◽  
Ternary Systems ◽  
Solubility Limit ◽  
Ternary Alloys ◽  
Energy Of Mixing ◽  
Free Energy Of Mixing

A thermodynamic analysis of the synthesis of face-centred cubic (fcc) and body-centred cubic (bcc) solid solutions of Ti-based alloys produced by mechanical alloying was performed. Four Ti-based alloys were analysed: (i) Ti-13Ta-3Sn (at.%), (ii) Ti-30Nb-13Ta (at.%), (iii) Ti-20Nb-30Ta (wt. %) and (iv) Ti-33Nb-4Mn (at.%). The milled powders were characterized by X-ray diffraction, and the crystallite size and microstrain were determined using the Rietveld and Williamson–Hall methods. The Gibbs free energy of mixing for the formation of a solid solution of the three ternary systems (Ti-Ta-Sn, Ti-Nb-Ta and Ti-Nb-Mn) was calculated using an extended Miedema’s model, applying the Materials Analysis Applying Thermodynamics (MAAT) software. The values of the activity of each component were determined by MAAT. It was found that increasing the density of crystalline defects, such as dislocations and crystallite boundaries, changed the solubility limit in these ternary systems. Therefore, at longer milling times, the Gibbs free energy increases, so there is a driving force to form solid solutions from elemental powders. Finally, there is agreement between experimental and thermodynamic data confirming the formation of solid solutions.

Effect of Niobium on the Structure and Photoactivity of Anatase (TiO2) Nanoparticles

2006 ◽  
Vol 6 (3) ◽  
pp. 762-770 ◽  
Author(s):  
Masanori Hirano ◽  
Kazumasa Matsushima
Keyword(s):  
Methylene Blue ◽  
Photocatalytic Activity ◽  
Solid Solutions ◽  
Uv Light ◽  
Anatase Tio2 ◽  
Hydrothermal Conditions ◽  
Niobium Content ◽  
Uv Light Irradiation ◽  
Adsorption Amount ◽  
Hydrolysis Of

Anatase-type TiO2 nanoparticles doped with 0–30 mol% niobium were directly formed from precursor solutions of TiOSO4 and NbCl5 under mild hydrothermal conditions at 120–180 °C for 5 h using the hydrolysis of urea. When the niobium content increased from 0 to 30 mol%, the crystallite size of anatase increased from 8.5 to 19 nm. The band gap of anatase was slightly decreased by making solid solutions with niobium. Their photocatalytic activity and adsorptivity were evaluated separately by the measurement of the concentration of methylene blue (MB) remained in the solution after maintained in the dark or under UV-light irradiation. To form anatase-type solid solutions by doping 5–15 mol% niobium into TiO2 was effective for improvement of the photoactivity of TiO2. The photocatalytic activity (the photooxidation rate) and the adsorption amount of MB for the sample containing 15 mol% niobium became more than approximately nine times and six times as much as those of the hydrothermal anatase-type pure TiO2, respectively.

scholarly journals Influence of cation substitution on electrical conductivity of microcrystalline ceramics based on (Cu1-xAgx)7GeSe5I solid solutions

2021 ◽  
Vol 24 (02) ◽  
pp. 131-138
Author(s):  
I.P. Studenyak ◽  
◽  
A.I. Pogodin ◽  
V.I. Studenyak ◽  
T.O. Malakhovska ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Solid Solutions ◽  
Electronic Conductivity ◽  
Microstructural Analysis ◽  
Cation Substitution ◽  
Cationic Sublattice ◽  
Total Electrical Conductivity ◽  
Complex Process ◽  
Nonlinear Character ◽  
Average Size

Ceramic samples based on the microcrystalline powders (Cu1–хAgx)7GeSe5I (x = 0, 0.25, 0.5, 0.75, 1) were prepared by pressing them at the pressure close to 400 MPa and subsequent annealing at 873 K for 36 hours. Using the microstructural analysis, the average size of microcrystallites of these samples was determined. Investigation of electrical conductivity of ceramics based on (Cu1 хAgx)7GeSe5I solid solutions was carried out using the method of impedance spectroscopy in the frequency range from 10 Hz to 3×105 Hz and within the temperature range 293...383 K. Analysis of the Nyquist plots allowed determining the contributions of ionic and electronic components to the total electrical conductivity. The temperature dependence of ionic and electronic conductivity in Arrhenius coordinates is linear, which indicates their thermoactivation character. The compositional behaviour of ionic and electronic conductivity, as well as their activation energies have been studied. Their nonlinear character can be explained by the complex process of recrystallization and Cu+ ↔ Ag+ cation substitution within the cationic sublattice.

PHASE TRANSITIONS IN SOLID SOLUTIONS BASED ON CDAS2 AT PRESSURES UP TO 50 GPA

2021 ◽  
Vol 0 (1) ◽  
pp. 102-105
Author(s):  
A.V. TEBENKOV ◽  
◽  
G.V. SUKHANOVA ◽  
A.N. BABUSHKIN ◽  
◽  
...  
Keyword(s):  
Phase Transitions ◽  
Crystal Lattice ◽  
Solid Solutions ◽  
Electrical Resistance ◽  
Structural Changes ◽  
Electronic Conductivity ◽  
Charge Carriers ◽  
Lattice Stability ◽  
Diamond Anvils ◽  
The Impact

Research has been performed into baric dependences between electrical resistance and thermo-EMF of eutectic solid solutions based on cadmium diarsenide of various compositions (Cd0.97Zn0.03As2 and Cd0.95Zn0.05As2) at pressures from 16 to 50 GPa and room temperature. Pressures were created in a chamber with conducting diamond anvils that served as contacts with the sample. Structural changes were recorded by changing electrical resistance and thermo-EMF. When replacing cadmium atom, zinc forms closer bonds with arsenic, which must result in the crystal lattice strengthening and higher pressures of phase transitions. Solid solutions preserve phase transitions observed in pure cadmium diarsenide. An increase in the crystal lattice stability of the solutions is confirmed compared to initial cadmium diarsenide. It is shown that with an increase in the zinc concentration pressures of phase transitions are shifted into the zone of higher pressures. The compounds preserve electronic conductivity in the range of pressures under consideration. At pressures higher than 30 GPa the thermo-EMF values become close to zero. This may be due to both an increase on concentrations of minority charge carriers and the impact of additional donating levels in the forbidden zone of solid solutions.

Compounds and Solid Solutions Occurring in Nitride-Oxide Systems

1991 ◽  
Vol 47 ◽  
pp. 58-69 ◽  
Author(s):  
De Sheng Yan ◽  
T.S. Yen ◽  
W.Y. Sun
Keyword(s):  
Solid Solutions ◽  
Oxide Systems ◽  
Nitride Oxide

Electronic Conductivity of In2 O 3 Solid Solutions with ZrO2

1994 ◽  
Vol 141 (10) ◽  
pp. 2759-2768 ◽  
Author(s):  
K. Sasaki ◽  
H. P. Seifert ◽  
L. J. Gauckler
Keyword(s):  
Solid Solutions ◽  
Electronic Conductivity
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