Energetics of lanthanide cobalt perovskites: LnCoO<sub>3−δ</sub> (Ln = La, Nd, Sm, Gd)

Sahu, Sulata K.; Tănăsescu, Speranţa; Scherrer, Barbara; Marinescu, Cornelia; Navrotsky, Alexandra

doi:10.1039/c5ta03655k

Cited by 21 publications

(15 citation statements)

References 38 publications

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“…series [42], where the vacancies are compensated by the formation of Co 2+ cations. These Co 2+ cations constitute magnetic impurities, which have been shown recently to act as nucleation centers for the formation of higher spin states across the spin-state transition [11].…”

Section: Oxygen Contentmentioning

confidence: 99%

Microwave-Assisted Synthesis, Microstructure, and Magnetic Properties of Rare-Earth Cobaltites

et al. 2016

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Citation for published item:quti¡ errez eij sD tuli nd r doEqonj lD tes¡ us nd ¡ evil fr ndeD h vid nd erryD s n nd wor¡ nD imilio nd hmidtD iner @PHIUA 9wi row veE ssisted synthesisD mi rostru tureD nd m gneti properties of r reEe rth o ltitesF9D snorg ni hemistryFD ST @IAF ppF TPUETQQF Further information on publisher's website:This document is the Accepted Manuscript version of a Published Work that appeared in nal form in Inorganic Chemistry, copyright c 2016 American Chemical Society after peer review and technical editing by the publisher. To access the nal edited and published work see https://doi.org/10.1021/acs.inorgchem.6b02557. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe series of perovskite rare-earth (RE) doped cobaltites (RE)CoO3 (RE = La -Dy) was prepared by microwave-assisted synthesis. The crystal structure undergoes a change of symmetry depending on the size of the RE cation. LaCoO3 is rhombohedral, S.G. , while for the rest of the RE series (Pr -Dy) the symmetry is orthorhombic, S.G. Pnma (No. 62). The crystal structure obtained by X-Ray diffraction was confirmed by high resolution transmission electron microscopy, which yielded a good match between experimental and simulated images. It is further shown that the well-known magnetism in LaCoO3, which involves a thermally induced Co 3+ (d 6 ) low spin to intermediate or high spin state transition, is strongly modified by RE-doping and a rich variety of magnetic order has been detected across the series.

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Section: Oxygen Contentmentioning

confidence: 99%

Microwave-Assisted Synthesis, Microstructure, and Magnetic Properties of Rare-Earth Cobaltites

et al. 2016

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“…This could reflect the smaller radius of Ce 3+ (1.34 Å) than of La 3+ (1.36 Å) for 12-fold coordination (Shannon 1976). Figure 2 shows a linear trend between the enthalpy of formation and the Goldschmidt tolerance factor, where the enthalpies of formation become more negative as the tolerance number increases, as has been noted before for many other perovskite systems (Sahu et al 2015).…”

Section: Enthalpies Of Formationmentioning

confidence: 70%

“…As in prior work (Sahu et al 2015), we use the 12-fold coordination number to calculate the tolerance number. The reasoning behind this is that the tolerance factor, calculated for the cubic case, shows the driving force both for distortion and for overall decrease in stability.…”

Section: Enthalpies Of Formationmentioning

confidence: 99%

Thermochemistry of rare earth perovskites Na₃_xRE₀_.₆₇₋_xTiO₃(RE = La, Ce)

Feng

Maram

Mielewczyk‐Gryń

et al. 2016

American Mineralogist

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High-temperature oxide melt solution calorimetry using sodium molybdate (3Na 2 O·4MoO 3 ) solvent at 973 K was performed for the Na 3x RE 0.67-x TiO 3 (RE = La, Ce) perovskite series. The enthalpies of formation of lanthanum perovskites from oxides (La 2 O 3 , Na 2 O, TiO 2 ), are -107.25 ± 2.56, -93.83 ± 6.06, -80.68 ± 5.93, and -33.49 ± 4.26 kJ/mol and enthalpies of formation from elements are -1614.05 ± 5.37, -1596.44 ± 7.68, -1594.03 ± 7.58, and -1577.56 ± 6.36 kJ/mol for Na 0.459 La 0.522 Ti 0.999 O 3 , Na 0.454 La 0.523 Ti 0.994 O 3 , Na 0.380 La 0.567 Ti 0.980 O 3 , and La 0.692 Ti 0.979 O 3 , respectively. The enthalpies of formation of cerium perovskites are -99.98 ± 5.78 and -45.78 ± 3.30 kJ/mol from oxides (Ce 2 O 3 , Na 2 O, TiO 2 ), and -1611.34 ± 6.90 and -1602.06 ± 2.72 kJ/mol from elements for Na 0.442 Ce 0.547 Ti 0.980 O 3 and Ce 0.72 Ti 0.96 O 3 .The A-site defect perovskites become more stable relative to oxide components as sodium contents increase. Na 0.5 Ce 0.5 TiO 3 and Na 0.5 La 0.5 TiO 3 could be considered as thermodynamically stable end-members in natural loparite minerals, in which these end-members are in solid solution with CaTiO 3 and other components.

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“…The drop solution enthalpies of the hydrated and anhydrous potassium niobate samples in molten sodium molybdate (3Na 2 OÁ4MoO 3 ) at 702°C were measured in a custommade isoperibol Tian-Calvet twin microcalorimeter described previously. [25][26][27][28] The calorimeter assembly was flushed with oxygen at 43 mL/min, and oxygen was bubbled through the solvent at 4.5 mL/min to aid dissolution and maintain oxidizing conditions. Pellets of approximately 5 mg were loosely pressed, weighed, and dropped from room temperature into the solvent in a platinum crucible in the calorimeter.…”

Section: Characterizationmentioning

confidence: 99%

Formation and Dehydration Enthalpy of Potassium Hexaniobate

2016

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The formation energetics of hydrous and dehydrated potassium hexaniobates are investigated using high‐temperature oxide melt solution calorimetry. The enthalpies of formation of K4Nb6O17 and K4Nb6O17·3H2O from oxides are (−864.42 ± 10.63) and (−899.32 ± 11.48) kJ/mol, respectively. The formation enthalpy of K4Nb6O17 from elements is (−7289.64 ± 12.50) kJ/mol, and of K4Nb6O17·3H2O is (−8181.94 ± 13.24) kJ/mol. The enthalpy of dehydration (ΔHdehy) for the reaction K4Nb6O17·3H2O (xl, 25°C) = K4Nb6O17 (xl, 25°C) + 3H2O (l, 25°C) is endothermic and is 34.60 ± 7.56 kJ/mol. The ΔHdehy per mole of water, 11.53 ± 2.52 kJ/mol, indicates the water molecules in K4Nb6O17·3H2O are not just physically adsorbed, but loosely bonded in the K4Nb6O17 phase, presumably in specific interlayer sites. The loss of this water near 100°C on heating is consistent with the weak bonding of water.

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Energetics of lanthanide cobalt perovskites: LnCoO_3−δ (Ln = La, Nd, Sm, Gd)

Abstract: The thermodynamic stability of lanthanide cobaltites is also a function of their existing oxygen non-stoichiometry.

Cited by 21 publications

References 38 publications

Microwave-Assisted Synthesis, Microstructure, and Magnetic Properties of Rare-Earth Cobaltites

Microwave-Assisted Synthesis, Microstructure, and Magnetic Properties of Rare-Earth Cobaltites

Thermochemistry of rare earth perovskites Na₃_xRE₀_.₆₇₋_xTiO₃(RE = La, Ce)

Formation and Dehydration Enthalpy of Potassium Hexaniobate

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Energetics of lanthanide cobalt perovskites: LnCoO3−δ (Ln = La, Nd, Sm, Gd)

Abstract: The thermodynamic stability of lanthanide cobaltites is also a function of their existing oxygen non-stoichiometry.

Cited by 21 publications

References 38 publications

Microwave-Assisted Synthesis, Microstructure, and Magnetic Properties of Rare-Earth Cobaltites

Microwave-Assisted Synthesis, Microstructure, and Magnetic Properties of Rare-Earth Cobaltites

Thermochemistry of rare earth perovskites Na3xRE0.67−xTiO3(RE = La, Ce)

Formation and Dehydration Enthalpy of Potassium Hexaniobate

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Energetics of lanthanide cobalt perovskites: LnCoO_3−δ (Ln = La, Nd, Sm, Gd)

Thermochemistry of rare earth perovskites Na₃_xRE₀_.₆₇₋_xTiO₃(RE = La, Ce)