Ionic transport in LiNbO3

1991 ◽  
Vol 6 (4) ◽  
pp. 851-854 ◽  
Author(s):  
Apurva Mehta ◽  
Edward K. Chang ◽  
Donald M. Smyth
Keyword(s):  
Ionic Conductivity ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Ionic Transport ◽  
Ionic Transport Number ◽  
Cell Measurement ◽  
Experimental Validity ◽  
Pressure Independent ◽  
Temperature Equilibrium ◽  
Good Agreement

The high temperature equilibrium conductivity (950 °C–1050 °C) of congruent LiNbO3 can be resolved into two components: an electronic portion that is dependent on the oxygen partial pressure and an ionic portion that is pressure independent. It is shown that the two components can be obtained from an analysis of the total equilibrium conductivity measured as a function of oxygen partial pressure. The ionic transport number (fractional ionic conductivity) thus obtained is compared with that obtained from an oxygen concentration cell measurement. The two techniques are found to be in excellent agreement, confirming the experimental validity of the defect chemistry method. From the temperature dependence of the ionic conductivity, the activation energy (138 kJ/mol [1.43 eV]) for the ionic transport is obtained. The results are in good agreement with the value previously obtained for the oxygen chemical diffusivity.

THE ELECTRICAL PROPERTIES OF ALUMINA AT HIGH TEMPERATURES

1966 ◽  
Vol 44 (8) ◽  
pp. 1685-1698 ◽  
Author(s):  
T. Matsumura
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Single Crystal ◽  
Transport Number ◽  
Ionic Transport ◽  
Mixed Conductor ◽  
Polycrystalline Alumina ◽  
Ionic Transport Number

The ionic transport number and the d-c. electrical conductivity of single-crystal and polycrystalline alumina have been studied between 1 000 °K and 1 750 °K at an oxygen partial pressure of 0.2 atm. The ionic transport number was determined by the galvanic-cell e.m.f. measurements; the electrical conductivity was measured by the three-terminal method.It was found that alumina is a mixed conductor, being predominantly an ionic conductor at temperatures below 1 100 °K and predominantly electronic at temperatures higher than 1 600 °K. The activation energies found for the electrical conductivity of the single-crystal and polycrystalline specimens are 0.8 eV and 2.4 eV respectively in the ionic range and 3.0 eV and 3.7 eV in the electronic range.

scholarly journals Wet Oxidation of Dairy Sewage

2012 ◽  
Vol 19 (1) ◽  
pp. 29-38
Author(s):  
Klara Piotrowska ◽  
Mirosław Imbierowicz ◽  
Andrzej Chacuk
Keyword(s):  
Kinetic Model ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Organic Compounds ◽  
Reduction Rate ◽  
Kinetic Studies ◽  
Wet Oxidation ◽  
Tank Reactor ◽  
Good Agreement

Wet Oxidation of Dairy Sewage Results of kinetic studies on the process of wet oxidation of dairy sewage are presented. Experiments were carried out in a stirred batch tank reactor at the oxygen partial pressure equal to 1 MPa and at temperature ranging from 473 to 523 K. Dairy sewage was subjected to oxidation at a natural pH close to 4. The efficiency of decomposition of organic compounds was estimated on the basis of TOC measurement. The highest TOC reduction rate reached 79.6%. A kinetic model of the process was proposed and its parameters were determined experimentally. Good agreement of the experimental and calculated results was obtained.

scholarly journals Transport Properties of Film and Bulk Sr0.98Zr0.95Y0.05O3−δ Membranes

2020 ◽  
Vol 10 (7) ◽  
pp. 2229 ◽  
Author(s):  
Adelya Khaliullina ◽  
Liliya Dunyushkina ◽  
Alexander Pankratov
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Transport Properties ◽  
Effective Conductivity ◽  
Ionic Transport ◽  
Transport Numbers ◽  
Pressure Gradients ◽  
Solution Deposition ◽  
Bulk Membrane ◽  
The Relationship

In electrode-supported solid oxide fuel cells (SOFCs) with a thin electrolyte, the electrolyte performance can be affected by its interaction with the electrode, therefore, it is particularly important to study the charge transport properties of thin electrode-supported electrolytes. The transport numbers of charged species in Ni-cermet supported Sr0.98Zr0.95Y0.05O3−δ (SZY) membranes were studied and compared to those of the bulk membrane. SZY films of 2.5 μm thickness were fabricated by the chemical solution deposition technique. It was shown that the surface layer of the films contained 1.5–2 at.% Ni due to Ni diffusion from the substrate. The Ni-cermet supported 2.5 μm-thick membrane operating in the fuel cell mode was found to possess the effective transport number of oxygen ions of 0.97 at 550 °C, close to that for the bulk SZY membrane (0.99). The high ionic transport numbers indicate that diffusional interaction between SZY films and Ni-cermet supporting electrodes does not entail electrolyte degradation. The relationship between SZY conductivity and oxygen partial pressure was derived from the data on effective conductivity and ionic transport numbers for the membrane operating under two different oxygen partial pressure gradients—in air/argon and air/hydrogen concentration cells.

The interfacial reaction in Cr3C2/Al2O3 composites

1999 ◽  
Vol 14 (3) ◽  
pp. 817-823 ◽  
Author(s):  
Ding-Fwu Lii ◽  
Jow-Lay Huang ◽  
Jin-Jay Huang ◽  
Horng-Hwa Lu
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Interfacial Reaction ◽  
Experimental Analysis ◽  
Computer Assisted ◽  
Sintering Atmosphere ◽  
Gas Concentration ◽  
Equilibrium Oxygen ◽  
Equilibrium Oxygen Partial Pressure ◽  
Good Agreement

This study investigates the effects of sintering atmosphere and temperature on the interfacial properties of Cr3C2/Al2O3 composites. Thermodynamic considerations and calculations with computer-assisted methods for the equilibrium compositions in the Al–O–Cr–C system were used to simulate the interfacial reaction in Cr3C2/Al2O3 composite during sintering. The results were in good agreement with the experimental analysis. Cr3C2 is more stable during sintering in a system with carbon due to the lower equilibrium oxygen partial pressure. Controlling CO and O2 gas concentration, Cr3C2 first oxidized, decarbonized, and then transformed to Cr7C3 before reacting with Al2O3. An interfacial reaction between Cr3C2 and Al2O3 was not observed.

Electrical Conductivity of Piezoelectric Strontium Bismuth Titanate Under Controlled Oxygen Partial Pressure

1999 ◽  
Vol 604 ◽  
Author(s):  
C. Voisard ◽  
P. Duran Martin ◽  
D. Damjanovic ◽  
N. Settier
Keyword(s):  
Electrical Conductivity ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Elevated Temperatures ◽  
Vacancy Concentration ◽  
Common Mechanism ◽  
Oxygen Vacancy Concentration ◽  
Reducing Conditions ◽  
Ionic Transport Number ◽  
Mn Doped

AbstractHysteresis free and linear piezoelectric behavior of SrBi4Ti4O15 (SrBIT) is very promising for precise sensors/actuators devices. Despite a quite low longitudinal piezoelectric coefficient (around 15 pC/N), its elevated ferroelectric phase transition temperature (540°C) allows its use above 300°C. Electrical conductivity at such temperatures should be kept as low as possible in order to avoid loss of piezoelectric properties or charge drifts. Under reducing conditions, however, the electrical conductivity may change considerably. The electrical conductivity of SrBi4Ti4O15 (SrBIT) has been measured under controlled oxygen partial pressure at elevated temperatures (700-900°C) from 1 atm down to 10−15atm. From 1 atm down to 10−15 atm pO2, above 700°C, the conductivity of SrBIT exhibits a -1/4 slope in log-log scale indicating n-type conductivity and an impurity controlled oxygen vacancy concentration. A conductivity minimum is observed around 0.2 atm for undoped SrBIT at 800°C. Acceptor doping (Mn) raises the minimum and flattens the conductivity curve with slope around -1/10 at 700°C, and -1/6 at 900°C. Ionic conductivity and defect ionization are discussed to account for this. Preliminary results indicate the possibility of a large, pO2 independent, region, down to 10−15atm pO2. The ionic transport number was found to be 0.42 at 800°C for undoped SrBIT and 0.75 for Mn doped SrBIT. The activation energies of undoped (1.35 eV) and Mn doped (1.44 eV) samples are close to each other as expected for a common mechanism

Creep Behavior Analysis for a Bilayer Functional Graded Electrolyte Supported High Temperature Ceramic Fuel Cells

2006 ◽  
Author(s):  
Gang Ju ◽  
Kenneth Reifsnider
Keyword(s):  
Fuel Cell ◽  
Ionic Conductivity ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Creep Behavior ◽  
Edge Crack ◽  
Porous Electrodes ◽  
Lattice Expansion ◽  
Anode Side ◽  
Ceramic Fuel

Ceramic fuel cell, such as solid oxide fuel cell (SOFC), usually has three functional layers with one dense electrolyte in the middle and two porous electrodes on each side of it, which operates around 1000°C. Recent research activities in SOFC tend to lower the operation temperature to the range of 700°C-800°C due to improvement in mechanical properties, and reduction in costs. However, the state-of-the-art electrolyte yttria-stabilized zirconia (YSZ) under this reduced temperature produces relatively poor ionic conductivity. Ceria-based electrolyte is an excellent candidate in electrical properties under intermediate temperature range, even though it shows a lattice expansion by cerium reduction at the very low oxygen partial pressure occurring at the anode side. Hence, a bilayer yttria doped ceria (YDC) with thin YSZ protection at anode side is designed to maximize the ionic conductivity. However, this lattice expansion of cerium results in an internal stress under this SOFC consideration. In this paper, oxygen partial pressure dependent creep behavior of an edge crack at the bi-material interface (YSZ:YDC) is studied numerically. The steady state C* path independent integral is obtained from ABAQUS code. Bi-material and homogeneous cases are discussed under extensive creep. Finally, fracture analysis of an edge crack at the bilayer electrolyte is also investigated for homogeneous bilayer materials.

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