Structure, stoichiometry, and phase purity of calcium substituted lanthanum manganite powders

Journal Article · Sun Nov 01 04:00:00 EST 1998 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1998.7894· OSTI ID:305377

Faaland, S; Einarsrud, M A; Roermark, L; Hoeier, R; Grande, T ^[1]; Knudsen, K D ^[2]

---

1. Norwegian Univ. of Science and Technology, Trondheim (Norway)
2. ESRF, Grenoble (France)

Calcium-doped lanthanum manganite La{sub 1{minus}x}Ca{sub x}MnO{sub 3}, synthesized by the glycine/nitrate method, was characterized by high resolution synchrotron X-ray powder diffraction, electron diffraction, and infrared spectroscopy. A strong correlation was observed between the cooling rate from the calcination temperature and the powder quality, indicating the importance of a homogeneous oxygen stoichiometry. The structure refinement reveals that La{sub 1{minus}x}Ca{sub x}MnO{sub 3} with x = 0.2, 0.3, 0.4, and 0.6 has orthorhombic symmetry with space group Pnma. The MnO{sub 6} octahedra are fairly symmetrical, but the octahedra are tilted about 20{degree} relative to the ideal perovskite structure. Infrared spectroscopy revealed that only the O-Mn-O bending mode is significantly influenced by the substitution of La with Ca. In La{sub 0.8}Ca{sub 0.2}MnO{sub 3} the authors found diffraction evidence of a superstructure in domains in some of the grains. They propose that the superstructure in La{sub 0.8}Ca{sub 0.2}MnO{sub 3} is due to ordering of Ca{sup 2+} ions on A (La{sup 3+}) sites in the perovskite ABO{sub 3} structure.

• OSTI ID: 305377
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 140; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALCIUM OXIDES
CHEMICAL COMPOSITION
CRYSTAL STRUCTURE
ELECTRON DIFFRACTION
EXPERIMENTAL DATA
INFRARED SPECTRA
LANTHANUM OXIDES
MANGANESE OXIDES
X-RAY DIFFRACTION