On the Crystal Structures of the High-temperature Forms of Strontium and Barium Carbonate and Structurally Related Compounds.

Strømme, K. O.; George, John W.; Husebye, Steinar; Mikalsen, Øyvind; Southern, J. T.; Edlund, Kaj; Eliasen, Mogens; Herskind, Carsten; Laursen, Thomas Munk; Pedersen, Poul Møller

doi:10.3891/acta.chem.scand.29a-0105

Cited by 31 publications

(13 citation statements)

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“…Finally, based on our experience and the experimental data, the refinement indicated the presence of a small amount of a high‐temperature SrCO 3 phase with a rhombohedral structure, 33 presumably formed by reaction between Sr on the surface and CO 2 from the gas used. The observed and calculated neutron diffraction patterns in the final refinement involving SrCO 3 are presented in Fig.…”

Section: Resultsmentioning

confidence: 99%

Structural Behavior of Oxygen Permeable SrFe_0.2Co_0.8O_x Ceramic Membranes with and Without pO₂ Gradients

Maxey

Richardson

2005

Journal of the American Ceramic Society

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The oxygen partial pressure (pO2)‐dependent structural behaviors of two dense tubular ceramic membranes in composition SrFe0.2Co0.8Ox with cubic perovskite structure have been investigated by high‐temperature neutron powder diffraction: one in “static” mode and one in simulated‐operation mode in which one side of the membrane was exposed to air and the other side to reducing gases with variable pO2 levels. Rietveld analysis on data collected for the membrane without pO2 gradients showed that the perovskite is stable in pO2 down to ∼10−12 atm, and at ∼10−14 atm it starts to decompose into a three‐phase mixture containing layered intergrowth Ruddlesden–Popper phases Srn+1(Fe,Co)nOx with n=2 and 3, along with CoO with rocksalt structure. Similar phase evolution was observed when insufficient air flowed on the air side of the membrane exposed to a pO2 gradient. The data support a nonlinear model of oxygen content in perovskite across the membrane thickness, corresponding to a pO2 profile that is shallow inside and steep near the reducing side surface. Gas compositions measured with mass spectrometry indicated that oxygen is permeated from the air side to the reducing side of the membrane. The oxygen permeation fluxes at 900°C were estimated to be 0.4–0.9 sccm/cm2 for the ∼1 mm thick membrane containing perovskite, depending upon pO2 gradient.

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Section: Resultsmentioning

confidence: 99%

Structural Behavior of Oxygen Permeable SrFe_0.2Co_0.8O_x Ceramic Membranes with and Without pO₂ Gradients

Maxey

Richardson

2005

Journal of the American Ceramic Society

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“…R3m phase transition of BaCO 3 (Antao and Hassan, 2007). Furthermore, a weak endothermal signal with onset at 1252Ô2 K indicated the transformation into the cubic, high-temperature modification (Stromme, 1975).…”

Section: Thermal Analyses and Decomposition Behaviourmentioning

confidence: 96%

Synthetic norsethite, BaMg(CO₃)₂: revised crystal structure, thermal behaviour and displacive phase transition

et al. 2014

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The crystal structure of synthetic BaMg(CO3)2 whose mineral name is norsethite was re-investigated by single-crystal X-ray diffraction. Complementary in situ high- and low-temperature studies by means of vibrational spectroscopy (Raman, IR), powder X-ray diffraction techniques and thermal analyses were performed. Diffraction images (298 K) revealed weak superstructure reflections caused by the displacement of the O atoms in the earlier considered Rm structure model (a = 5.0212(9), cnew = 2 cold = 33.581(6) Å , Rc, Z = 6, R1 = 0.011, sinθ/λ < 0.99 Å –1). Thermal analyses reveal decarbonatization in two decomposition steps above 750 K, and the heat-flow curves (difference scanning calorimetry) give clear evidence of a weak and reversible endothermal change at 343±1 K. This agrees with a discontinuity in the IR and single-crystal Raman spectra. The changing trend of the c/a ratio supports this discontinuity indicating a temperature-induced structural transition in the range between 343 and 373 K. As the change of the unit-cell volume is almost linear, the character of the transition is apparently second order and matches the mechanism of a subtle displacement of the oxygen atom position. The apparent instability of the Rc structure is also evidenced by the remarkably larger anisotropic displacement of the oxygen atom.

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“…Additionally, a low amount of CoO can be observed in the powder. The carbonate remains in orthorhombic symmetry up to 973 K. Rising the temperature leads to the phase transition of the orthorhombic BaCO 3 to rhombohedral polymorph at 1073 K and to cubic carbonate phase at 1273 K. The high-temperature cubic carbonate (space group Fm3m) exists only at temperatures above 1233 K as reported by Strømme [23]. Interestingly, the integrated intensity of carbonate phase in the scan collected at 1073 K was diminished from 42% at 1073 K to 10% at 1273 K, which can be explained by strong decline of the carbonate content in the sample.…”

Section: Resultsmentioning

confidence: 54%

“…Structural data for the known phases were taken from ICSD database (FIZ Karlsruhe) with file numbers: BaCoO 2. 23 . Scanning TEM (STEM) was conducted at 200 kV on a JEOL JEM-2100 F-UHR field-emission instrument.…”

Section: Methodsmentioning

confidence: 95%

In-situ X-ray diffraction study of carbonate formation and decomposition in perovskite-type BCFZ

Efimov

Czuprat

Feldhoff

2011

Journal of Solid State Chemistry

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On the Crystal Structures of the High-temperature Forms of Strontium and Barium Carbonate and Structurally Related Compounds.

Cited by 31 publications

References 0 publications

Structural Behavior of Oxygen Permeable SrFe_0.2Co_0.8O_x Ceramic Membranes with and Without pO₂ Gradients

Structural Behavior of Oxygen Permeable SrFe_0.2Co_0.8O_x Ceramic Membranes with and Without pO₂ Gradients

Synthetic norsethite, BaMg(CO₃)₂: revised crystal structure, thermal behaviour and displacive phase transition

In-situ X-ray diffraction study of carbonate formation and decomposition in perovskite-type BCFZ

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On the Crystal Structures of the High-temperature Forms of Strontium and Barium Carbonate and Structurally Related Compounds.

Cited by 31 publications

References 0 publications

Structural Behavior of Oxygen Permeable SrFe0.2Co0.8Ox Ceramic Membranes with and Without pO2 Gradients

Structural Behavior of Oxygen Permeable SrFe0.2Co0.8Ox Ceramic Membranes with and Without pO2 Gradients

Synthetic norsethite, BaMg(CO3)2: revised crystal structure, thermal behaviour and displacive phase transition

In-situ X-ray diffraction study of carbonate formation and decomposition in perovskite-type BCFZ

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Product

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Structural Behavior of Oxygen Permeable SrFe_0.2Co_0.8O_x Ceramic Membranes with and Without pO₂ Gradients

Structural Behavior of Oxygen Permeable SrFe_0.2Co_0.8O_x Ceramic Membranes with and Without pO₂ Gradients

Synthetic norsethite, BaMg(CO₃)₂: revised crystal structure, thermal behaviour and displacive phase transition