Thermodynamic Stability and Microscopic Behavior of BaxSr1-xCo1-yFeyO3-δ Perovskites

The mixed conducting perovskite-type oxides BaxSr1-xCo1-yFeyO3-δ (BSCF) are intensively studied as potential high-performance solid oxide fuel cell cathode materials. The effect of different compositional variables and oxygen stoichiometry on the structure and thermodynamic stability of the BaxSr1-xCo1-yFeyO3-δ (x = 0.2, 0.4, 0.5, 0.6, 0.8; y = 0.2, 0.4, 0.6, 0.8, 1) perovskite-type compositions were investigated by solid electrolyte electrochemical cells method and scanning electron microscopy (SEM). The thermodynamic quantities represented by the partial molar free energies, enthalpies and entropies of oxygen dissolution in the perovskite phase, as well as the equilibrium partial pressures of oxygen were obtained in the temperature range of 823–1273 K. The in situ change of oxygen stoichiometry and the determination of thermodynamic parameters of the new oxygen-deficient BSCF compositions were studied via coulometric titration technique coupled with electromotive force (EMF) measurements. The effect of A- and B-site dopants concentration correlated to the variation of oxygen stoichiometry on the thermodynamic stability and morphology of the BSCF samples was evidenced.

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Thermodynamic Properties of Nano- and Micro-Structured Perovskite-Type Compounds

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.99-100.117 ◽

2004 ◽

Vol 99-100 ◽

pp. 117-122 ◽

Cited By ~ 1

Author(s):

S. Tanasescu ◽

C. Marinescu ◽

F. Maxim

Keyword(s):

Thermodynamic Properties ◽

Perovskite Phase ◽

Coulometric Titration ◽

Oxygen Stoichiometry ◽

Free Energies ◽

Nanocrystalline State ◽

Lanthanum Manganites ◽

Partial Pressures ◽

Abo3 Perovskite ◽

Perovskite Type

The thermodynamic properties of the ABO3 perovskite-type compounds are strongly affected by the A- and B- site substitution and the oxygen nonstoichiometry. The paper presents the thermodynamic properties of some doped nano- and microstructured lanthanum manganites of general formula La1-xMxMn1-yMeyO3 (where M=Sr, Ca; Me=Al; x=0.3;0.33, y=0;0.05) which have been studied within the temperature range of 873-1273 K in a reducing atmosphere (10-6 Pa). The relative partial molar free energies, enthalpies and entropies of oxygen dissolution in the perovskite phase and the equilibrium partial pressures of oxygen have been obtained by using a solid electrolyte galvanic cell method. The influence of the oxygen stoichiometry change on the thermodynamic properties was examined using the data obtained by a coulometric titration technique coupled with measurements of the electromotive force (EMF). The focus of the research was to emphasise modifications of the thermodynamic properties connected with the nanocrystalline state. The results obtained are discussed in relation to significant changes in the overall concentration of defects.

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Oxygen stoichiometry, unit cell volume, and thermodynamic quantities of perovskite-type oxides

Journal of Solid State Electrochemistry ◽

10.1007/s10008-006-0175-2 ◽

2006 ◽

Vol 11 (4) ◽

pp. 469-477 ◽

Cited By ~ 19

Author(s):

Egle Girdauskaite ◽

Helmut Ullmann ◽

Mahmoud Al Daroukh ◽

Vladimir Vashook ◽

Martin Bülow ◽

...

Keyword(s):

Cell Volume ◽

Unit Cell Volume ◽

Unit Cell ◽

Oxygen Stoichiometry ◽

Thermodynamic Quantities ◽

Perovskite Type

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Some Aspects of the Nonstoichiometric and Thermodynamic Behavior of the YBa2Cu3Oz System

MRS Proceedings ◽

10.1557/proc-156-83 ◽

1989 ◽

Vol 156 ◽

Cited By ~ 4

Author(s):

M. Tetenbaum ◽

L. Curtiss ◽

B. Czech ◽

B. Tani ◽

M. Blander

Keyword(s):

Low Temperature ◽

Oxygen Partial Pressure ◽

Partial Pressure ◽

Coulometric Titration ◽

Temperature Data ◽

Oxygen Stoichiometry ◽

Miscibility Gap ◽

Thermodynamic Behavior ◽

Partial Pressures ◽

Titration Technique

ABSTRACTThe nonstoichiometric and thermodynamic behavior of the YBa2Cu3Ox system as a function of oxygen partial pressure and temperature is being investigated by means of a coulometric titration technique. The oxygen content of the superconductor can be varied coulometrically by well-defined small amounts and the equilibrium partial pressures determined from the EMF. The oxygen stoichiometry in YBa2Cu3Ox as a function of oxygen partial pressure shows a change of curvature around x = 6.55–6.75 and an inflection around x ≅ 6.65 at temperatures between 400–500°C. These new low temperature data are consistent with the presence of a miscibility gap at lower temperatures, which is similar to that postulated in several theoretical papers.

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Oxygen Content and Thermodynamic Stability of YBaCo2O6−δ Double Perovskite

Advances in Materials Science and Engineering ◽

10.1155/2018/1205708 ◽

2018 ◽

Vol 2018 ◽

pp. 1-6 ◽

Cited By ~ 4

Author(s):

Anton L. Sednev ◽

Andrey Yu Zuev ◽

Dmitry S. Tsvetkov

Keyword(s):

Oxygen Content ◽

Thermodynamic Stability ◽

Crucial Role ◽

Coulometric Titration ◽

Stability Limit ◽

Double Perovskite ◽

Stability Diagram ◽

Partial Pressures ◽

The Stability ◽

Titration Technique

The thermodynamic stability of the double perovskite YBaCo2O6−δ was studied using the coulometric titration technique and verified by measurements of the overall conductivity depending on oxygen partial pressure at a given temperature. As a result, the stability diagram of YBaCo2O6−δ was plotted. YBaCo2O6−δ was found to be thermodynamically stable in air at 850°C and higher temperatures, whereas its thermodynamic stability at 900°C is limited by the range of oxygen partial pressures −3.56 ≤ log(pO2/atm) ≤ −0.14. Oxygen content in YBaCo2O6−δ slightly decreases at 900°C from 5.035 at log(pO2/atm) = −0.14 to 4.989 in the atmosphere with log(pO2/atm) = −3.565 indicating a crucial role which variation of Co+3/Co+2 ratio plays in its stability. YBaCo2O6−δ decomposes into the mixture of YCoO3 and BaCoO3−z at the high pO2 stability limit, whereas YBaCo4O7, BaCo1−xYxO3−γ, and Y2O3 were identified as the products of its decomposition at the low pO2 one.

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Influence of Composition and Particle Size on Spin Dynamics and Thermodynamic Properties of Magnetoresistive Perovskites

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2008.d127 ◽

2008 ◽

Vol 8 (2) ◽

pp. 914-923 ◽

Cited By ~ 3

Author(s):

Speranta Tanasescu ◽

Florentina Maxim ◽

Florina Teodorescu ◽

Liviu Giurgiu

Keyword(s):

Thermodynamic Properties ◽

Perovskite Phase ◽

Spin Dynamics ◽

Coulometric Titration ◽

Thermodynamic Characteristics ◽

Oxygen Stoichiometry ◽

Magnetic Characteristics ◽

Nanocrystalline State ◽

Redox Titration ◽

Paramagnetic Resonance

The thermodynamic behavior and spin dynamics of the colossal magnetoresistive (CMR) perovskites of general formula La1−x(A)xMn1−y(B)yO3 (where A is an alkaline earth, and B = Al, In) have been studied in order to evidence the effect of composition and the influence of nanocrystallinity on the thermodynamic and magnetic characteristics. By using electron paramagnetic resonance (EPR) spectroscopy, the behavior of the exchange coupling integral (J) between Mn spins and the polaron activation energy (Ea) have been investigated. The thermodynamic properties represented by the relative partial molar free energies, enthalpies and entropies of oxygen dissolution in the perovskite phase, as well as the equilibrium partial pressures of oxygen have been obtained by using solid electrolyte electrochemical cells method. The influence of the oxygen stoichiometry change on the thermodynamic properties was examined using the data obtained by a coulometric titration technique coupled with measurements of the electromotive force (EMF). The results were correlated with the average Mn valence values as determined by redox titration. The properties of the rare-earth manganites are strongly affected by the A- and B-site substitution and by the oxygen nonstoichiometry. New features related to the modifications in properties connected with the nanocrystalline state were evidenced. The correlation existing between the magnetic and thermodynamic characteristics were discussed in relation to significant changes in the overall concentration of defects.

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Determination of the ionization constant of water between 100 to 200°C by emf measurements, with some derived thermodynamic quantities

Electrochimica Acta ◽

10.1016/0013-4686(71)85005-3 ◽

1971 ◽

Vol 16 (3) ◽

pp. 315-338 ◽

Cited By ~ 14

Author(s):

J.V. Dobson ◽

H.R. Thirsk

Keyword(s):

Ionization Constant ◽

Thermodynamic Quantities ◽

Emf Measurements

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Pr-Doping Motivating the Phase Transformation of the BaFeO3-δ Perovskite as a High-Performance Solid Oxide Fuel Cell Cathode

ACS Applied Materials & Interfaces ◽

10.1021/acsami.1c03514 ◽

2021 ◽

Author(s):

Yunjie Gou ◽

Guangdong Li ◽

Rongzheng Ren ◽

Chunming Xu ◽

Jinshuo Qiao ◽

...

Keyword(s):

Phase Transformation ◽

Fuel Cell ◽

Solid Oxide Fuel Cell ◽

High Performance ◽

Solid Oxide ◽

Oxide Fuel ◽

Fuel Cell Cathode ◽

Cell Cathode

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Controlled partial melting during isobaric and isothermal processing of dipcoated Bi-2212/Ag tapes

Journal of Materials Research ◽

10.1557/jmr.1998.0487 ◽

1998 ◽

Vol 13 (12) ◽

pp. 3580-3586 ◽

Cited By ~ 3

Author(s):

A. L. Crossley ◽

J. L. MacManus-Driscoll

Keyword(s):

Phase Diagram ◽

Oxygen Partial Pressure ◽

Partial Pressure ◽

Partial Melting ◽

Coulometric Titration ◽

Processing Route ◽

Optimum Processing ◽

Partial Pressures ◽

Titration Technique

A detailed study has been made of the control and optimization of partial melting of dipcoated Bi2Sr2Ca1Cu2O8+δAg0.1 (Bi-2212) tapes using reduced oxygen partial pressures. A coulometric titration technique has been employed to vary the oxygen partial pressure in a region of the phase diagram corresponding to binary melting, and the amount of partial melting has been quantified. Using this information, tapes have been processed using both isothermal and isobaric techniques. An optimum processing route was determined which combined isothermal and isobaric processes. Highly aligned material at the point of optimum melting was obtained.

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