The correlation between the crystallization field of Y3Fe5O12 and the Oxygen Ion Concentration of High-temperature Solvents

1988 ◽  
Vol 23 (1) ◽  
pp. K1-K5 ◽  
Author(s):  
K. Fischer ◽  
E. Sinn
Keyword(s):  
High Temperature ◽  
Crystallization Field ◽  
Ion Concentration ◽  
Oxygen Ion

Structural features and enhanced high-temperature oxygen ion transport in SrFe1−xTaxO3−δ

2013 ◽  
Vol 197 ◽  
pp. 191-197 ◽  
Author(s):  
Alexey A. Markov ◽  
Elizaveta V. Shalaeva ◽  
Alexander P. Tyutyunnik ◽  
Vasily V. Kuchin ◽  
Mikhail V. Patrakeev ◽  
...  
Keyword(s):  
High Temperature ◽  
Ion Transport ◽  
Structural Features ◽  
Oxygen Ion

YBa2Cu3O7–x:Transport Properties and Defects at High Temperature

1989 ◽  
Vol 44 (12) ◽  
pp. 1167-1171 ◽  
Author(s):  
G. Chiodelli ◽  
G. Campari-Viganò ◽  
G. Flor
Keyword(s):  
Electrical Resistivity ◽  
High Temperature ◽  
Tetragonal Phase ◽  
Orthorhombic Phase ◽  
Ion Migration ◽  
Resistivity Measurements ◽  
Oxygen Ion ◽  
Partial Pressures ◽  
Oxygen Ion Migration ◽  
The One

Abstract Electrical resistivity measurements were carried out on polycrystalline YBa2Cu3O7-x at temperatures 300 < T < 1023 K and oxygen partial pressures 5 ·10-7 ≤ po2 ≤ 1 atm. The samples, equilibrated in the range from 5 ·10-4 to 1 atm, show metallic behaviour, the one equilibrated at po2 = 2 ·10-5 shows a transition between metallic and semiconducting behaviour at 920 K, and that equilibrated at po2 = 5 ·10-7 shows semiconducting behaviour: for the latter the relevant resistivity is due to the oxygen-ion migration. The isotherms log σ vs. log po2 (in the temperature range from 723 to 1023 K) show slopes of about 1/6 at 723 K (orthorhombic phase) and about 1/2 at 1023 K (tetragonal phase). These results are discussed in terms of appropriate defect models.

scholarly journals Leakage Current Degradation Due to Ion Drift and Diffusion in Tantalum and Niobium Oxide Capacitors

2017 ◽  
Vol 24 (2) ◽  
pp. 255-264 ◽  
Author(s):  
Martin Kuparowitz ◽  
Vlasta Sedlakova ◽  
Lubomir Grmela
Keyword(s):  
High Temperature ◽  
Electric Field ◽  
Leakage Current ◽  
Niobium Oxide ◽  
Ion Concentration ◽  
Homogeneous Distribution ◽  
Insulating Layer ◽  
Ion Drift ◽  
Positive Ions ◽  
And Diffusion

AbstractHigh temperature and high electric field applications in tantalum and niobium capacitors are limited by the mechanism of ion migration and field crystallization in a tantalum or niobium pentoxide insulating layer. The study of leakage current (DCL) variation in time as a result of increasing temperature and electric field might provide information about the physical mechanism of degradation. The experiments were performed on tantalum and niobium oxide capacitors at temperatures of about 125°C and applied voltages ranging up to rated voltages of 35 V and 16 V for tantalum and niobium oxide capacitors, respectively. Homogeneous distribution of oxygen vacancies acting as positive ions within the pentoxide layer was assumed before the experiments. DCL vs. time characteristics at a fixed temperature have several phases. At the beginning of ageing the DCL increases exponentially with time. In this period ions in the insulating layer are being moved in the electric field by drift only. Due to that the concentration of ions near the cathode increases producing a positively charged region near the cathode. The electric field near the cathode increases and the potential barrier between the cathode and insulating layer decreases which results in increasing DCL. However, redistribution of positive ions in the insulator layer leads to creation of a ion concentration gradient which results in a gradual increase of the ion diffusion current in the direction opposite to the ion drift current component. The equilibrium between the two for a given temperature and electric field results in saturation of the leakage current value. DCL vs. time characteristics are described by the exponential stretched law. We found that during the initial part of ageing an exponent n = 1 applies. That corresponds to the ion drift motion only. After long-time application of the electric field at a high temperature the DCL vs. time characteristics are described by the exponential stretched law with an exponent n = 0.5. Here, the equilibrium between the ion drift and diffusion is achieved. The process of leakage current degradation is therefore partially reversible. When the external electric field is lowered, or the samples are shortened, the leakage current for a given voltage decreases with time and the DCL vs. time characteristics are described by the exponential stretched law with an exponent n = 0.5, thus the ion redistribution by diffusion becomes dominant.

Applicability of Gd0.9Ca0.1AlO3-δ Ceramic Electrolyte for Intermediate Temperature Solid Oxide Fuel Cells

2012 ◽  
Vol 476-478 ◽  
pp. 1785-1789 ◽  
Author(s):  
Gui Hua Liu ◽  
Fang Wang ◽  
Rui Qiang Yan
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Solid Oxide Fuel Cells ◽  
Solid Oxide ◽  
Intermediate Temperature ◽  
Pure Oxygen ◽  
Electrode Polarization ◽  
Oxide Fuel ◽  
Ceramic Electrolyte ◽  
Oxygen Ion

In this paper, the applicability of Gd0.9Ca0.1AlO3-δ (GCAO) oxygen-ion conductor as ceramic electrolyte for intermediate temperature solid oxide fuel cells (SOFCs) was systematically investigated. XRD and TGA results demonstrate that GCAO material is in possession of sufficient structural stability from low to high temperature, desirable chemical stability against humidified reducing atmosphere and fine high-temperature thermal stability in air. Thermal shrinkage research during high temperature sintering shows that complete sintering of pressed green GCAO disk is around 1500 oC and the corresponding thermal expansion coefficient of sintered GCAO is 9.2×10-6 K-1 from room temperature to 1000 oC. In addition, total conductivity of GCAO ranges from 0.00073 to 0.0081 S•cm-1 in air as function of temperature increasing from 600 to 800 oC where the corresponding activation energy is determined as 96.19 KJ•mol-1. A 2-mm-thick electrolyte-supported single fuel cell was prepared with La0.8Sr0.2TiO3-δ/Ce0.8Gd0.2O2-δ and La0.8Sr0.2MnO3-δ/Ce0.8Gd0.2O2-δ as anode and cathode, and tested at 800 oC with humidified hydrogen and static air as fuel and oxidizer, respectively. The OCV reaches as high as 1.1 V which prove the pure oxygen-ion conduction of GCAO; and the corresponding maximum output and electrode polarization resistance reach 42 mW/cm2 and 0.15 Ώcm2, respectively. In summary, GCAO could be a possible electrolyte candidate for intermediate temperature SOFCs.

Theoretical Calculation of the Electrical Potential at the Electrode/Electrolyte Interfaces of Solid Oxide Fuel Cells

2005 ◽  
Vol 2 (4) ◽  
pp. 238-245 ◽  
Author(s):  
Ismail Celik ◽  
S. Raju Pakalapati ◽  
Maria D. Salazar-Villalpando
Keyword(s):  
Free Energy ◽  
Fuel Cells ◽  
Solid Oxide Fuel Cells ◽  
Electrical Potential ◽  
Solid Oxide ◽  
Ion Concentration ◽  
Oxide Fuel ◽  
Oxygen Ion ◽  
Proposed Model ◽  
Semi Empirical

A new semi-empirical model is formulated to calculate the potential differences at the cathode/electrolyte and electrolyte/anode interfaces separately for solid oxide fuel cells. The new model is based on a reduced reaction mechanism, and it accounts for the oxygen ion concentration at these interfaces. The model also considers the Gibbs free energy for the two electrode interfaces seperately. Results from case studies demonstrate the great potential of the proposed model

737. The heat coagulation of milk: II. variations in sensitivity of casein to calcium ions

1958 ◽  
Vol 25 (3) ◽  
pp. 467-474 ◽  
Author(s):  
G. T. Pyne
Keyword(s):  
High Temperature ◽  
Calcium Ions ◽  
Serum Proteins ◽  
Significant Part ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Temperature Stabilization ◽  
Phosphate Content ◽  
Hydrogen Ion Concentration ◽  
Phosphate Complex

1. The sensitivity to calcium of the caseinate-phosphate complex of milk heated at 120°C., increases to an early maximum and thereafter steadily declines, apparently in consequence of parallel changes in the sensitivity of its caseinate constituent.2. A simultaneously developed capacity of the heated complex to bind additional colloidal phosphate appears to be unrelated to these changes in casein sensitivity.3. Colloidal phosphate content is confirmed as a factor in the heat coagulation of milk.4. Heat-developed acidity contributes to the heat coagulation of milk primarily by increasing hydrogen-ion concentration and only slightly, if at all, through release of calcium ions from insoluble combinations.5. Neither serum proteins nor protein-lactose combinations play any significant part in the heat coagulation of milk.6. The bearing of these results on the heat coagulation of milk in general and on the operation of certain high-temperature stabilization treatments is discussed.

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