Oxygen non-stoichiometry, high-temperature properties, and phase diagram of CaMnO3–δ

Leonidova, Ekaterina I.; Леонидов, И. А.; Патракеев, М.В.; Кожевников, В. Л.

doi:10.1007/s10008-010-1288-1

Cited by 74 publications

(96 citation statements)

References 31 publications

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“…3 in Ref. [47] indicates that the intermediate tetragonal phase should be absent at perfect oxygen stoichiometry, which is the case treated in this paper. We may thus expect our results to be consistent with a single [17] is, to our knowledge, the only work which performed structural characterizations for all three phases.…”

Section: Discussion: Displacive Vs Order-disorder Phase Transitionmentioning

confidence: 74%

“…A few other things should be noted here: (1) Several experimental works have confirmed the presence of two structural phase transitions [46,47], whereas some other studies [48,49] find only a single orthorhombic-to-cubic phase transition without an intermediate tetragonal phase. The existence of the intermediate phase is likely related to oxygen deficiency [47]. In fact straightforward extrapolation of Fig.…”

Section: Discussion: Displacive Vs Order-disorder Phase Transitionmentioning

confidence: 87%

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Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Klarbring

Simak

2018

Phys. Rev. B

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The temperature-induced antiferrodistortive (AFD) structural phase transitions in CaMnO 3 , a typical perovskite oxide, are studied using first-principles density functional theory calculations. These transitions are caused by tilting of the MnO 6 octahedra that are related to unstable phonon modes in the high-symmetry cubic perovskite phase. Transitions due to octahedral tilting in perovskites normally are believed to fit into the standard soft-mode picture of displacive phase transitions. We calculate phonon-dispersion relations and potential-energy landscapes as functions of the unstable phonon modes and argue based on the results that the phase transitions are better described as being of order-disorder type. This means that the cubic phase emerges as a dynamical average when the system hops between local minima on the potential-energy surface. We then perform ab initio molecular dynamics simulations and find explicit evidence of the order-disorder dynamics in the system. Our conclusions are expected to be valid for other perovskite oxides, and we finally suggest how to predict the nature (displacive or order-disorder) of the AFD phase transitions in any perovskite system.

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Section: Discussion: Displacive Vs Order-disorder Phase Transitionmentioning

confidence: 74%

Section: Discussion: Displacive Vs Order-disorder Phase Transitionmentioning

confidence: 87%

Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Klarbring

Simak

2018

Phys. Rev. B

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“…Thermodynamic functions of oxygen, ΔH O and ΔS O , are known to be very sensitive to changes of oxygen content in the structure and, therefore, can provide rather detailed information on defect equilibria in non-stoichiometric oxides [21][22][23][24]. Hence, the present work was aimed at calculation of partial molar thermodynamic functions of oxygen in CаMnO 3−δ from the earlier obtained experimental data [17] with the use of defect formation reactions (1) and (2). The relation of the thermodynamic functions of oxygen with defect formation parameters is found, and it is shown that changes in ΔH O and ΔS O directly reflect development of reaction (2) at heating.…”

Section: +mentioning

confidence: 99%

“…The chemical potential of oxygen Δμ O (δ,T ) in CаMnO 3−δ relative to the standard state can be calculated from the pressure-dependent isotherms δ [17] as…”

Section: Partial Molar Enthalpy and Entropy Of Oxygenmentioning

confidence: 99%

“…The authors used experimental isotherms (3−δ) vs. log p O 2 for calculations of partial molar enthalpy ΔH O and entropy ΔS O of oxygen in СаMnO 3−δ at temperatures within 950-1050°С where the cubic structure is stable. More recently [17], we carried out measurements of the p O 2 -Т-δ diagram at lower temperatures 700-950°С where all three known hightemperature modifications (orthorhombic, tetragonal and cubic) of СаMnO 3−δ can exist. The attempts proved unsuccessful to simulate the diagram based on the traditional assumption that only a reaction of oxygen exchange…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamics of oxygen in CaMnO3 − δ

Goldyreva

Леонидов

Патракеев

et al. 2013

J Solid State Electrochem

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The experimental data for equilibrium oxygen content were used in order to extract increments of partial molar thermodynamic functions of oxygen with changes of oxygen stoichiometry in calcium manganite CaMnO 3−δ . It is shown that along with the oxygen exchange reaction, thermal excitation of Mn 4+ cations plays an important role in equilibration of charged manganese species that appear in response to the loss of oxygen at heating. The interrelation of partial molar enthalpy and entropy of oxygen with electron and ion defect formation parameters is obtained in approximation of the point defect model. The nearly linear changes of oxygen partial molar enthalpy are shown to directly reflect thermally driven changes in concentration of Mn 3+ cations.

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Reticulated Porous Perovskite Structures for Thermochemical Solar Energy Storage

Pein

Matzel

Oliveira

et al. 2022

Advanced Energy Materials

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In contrast to photovoltaics and wind turbines where solar/wind energy is converted directly to electrical power needing immediate supply to the grid, heat can be stored for long periods and supplied on demand. Through this inherent capability, CSP plants can play a crucial role on our transition from our current fossil fuels-based energy system to one based to a large extent on fluctuating power from renewable energy sources, being able to supply cost-effective, baseload and peak-load electricity and stabilizing the power grids. The approach set forth herein is targeted on increasing the storage density of air-operated CSP plants by hybridizing sensible with thermochemical storage of solar heat within the same storage unit volume, through the exploitation of reversible reduction-oxidation reactions of air in direct contact with porous ceramic structures made entirely of earth-abundant, inexpensive, nontoxic metal oxides. This approach is entirely compatible with the "modularity" and thus straightforward scalability of current state-of-the-art regenerative sensible heat storage/recovery systems that are manufactured from similar, yet chemically inert inexpensive porous structures like bricks and honeycombs.Historically, coupling redox (reduction-oxidation) chemistries operating on the transition between the oxidized (MeO x ) and the reduced state (MeO x-δ ) of a metal oxide exhibiting multiple The inherent capability of concentrated solar power (CSP) plants for sensible thermal energy storage ensures their continuous operation and is considered their most crucial competitive edge versus other renewable energy sources. The storage density of air-operated CSP plants can be significantly increased by hybridizing sensible with thermochemical storage of solar heat, exploiting reversible air-solid oxide reduction-oxidation reactions. Thermochemical storage-relevant-protocols testing of in-house manufactured lab-scale reticulated porous ceramic foams made entirely of CaMnO 3 perovskite reveals fully reversible reduction-oxidation in up to 46 cycles between 300 and 1100 °C under air, without any deterioration of the foams' structural integrity and exploitable endothermic/exothermic heat effects between 890 and 920 °C linked to an orthorhombic-to-cubic phase transition. Dilatometry experiments with CaMnO 3 bars under identical cyclic conditions demonstrate the correlation of this phase transition to an increase in the thermal expansion coefficient but nevertheless, complete recovery of the initial specimen dimensions upon completion of a full heat-up/cooldown redox cycle. The possibility of shaping into sturdy reticulated porous ceramic structures which exhibit complete dimensional reversibility upon cyclic redox operation, combined with the low cost, earth abundance and environmentally benign character of the constituting elements, render such perovskite compositions extremely attractive for the manufacture of large-scale porous structured objects for exploitation in various thermochemical processes.

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Oxygen non-stoichiometry, high-temperature properties, and phase diagram of CaMnO3–δ

Cited by 74 publications

References 31 publications

Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Thermodynamics of oxygen in CaMnO3 − δ

Reticulated Porous Perovskite Structures for Thermochemical Solar Energy Storage

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