High-temperature structural phase transition in Ca{sub 2}Fe{sub 2}O{sub 5} studied by in-situ X-ray diffraction and transmission electron microscopy

Journal Article · Mon Jun 15 04:00:00 EDT 2009 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.03.027· OSTI ID:21370443

Krueger, Hannes ^[1]; Kahlenberg, Volker ^[1]; Petricek, Vaclav ^[2]; Phillipp, Fritz ^[3]; Wertl, Waltraud ^[1]

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1. Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, 6020 Innsbruck (Austria)
2. Institute of Physics, Academy of Sciences of the Czech Republic, v. v. i., Na Slovance 2, 182 21 Praha (Czech Republic)
3. Max Planck Institute for Metals Research, Stuttgart Center for Electron Microscopy, Heisenbergstrasse 3, 70569 Stuttgart (Germany)

Ca{sub 2}Fe{sub 2}O{sub 5} shows a first-order phase transition from space group Pnma to a modulated structure described in superspace group Imma(00gamma)s00. The transition starts at 947 K during heating and the reverse transition in cooling conditions starts at 923 K, as determined from differential thermal analysis. In-situ high-temperature single-crystal X-ray diffraction experiments revealed a phase coexistence over a range of ca. 25 K. Data collected in this range show a good fit to a combined model of the two simultaneously occurring phases, which was refined using the software JANA2006. In-situ high-temperature transmission electron microscopy (selected area diffraction, dark field and high resolution images) was utilized to prove the existence of Pnma and Imma(00gamma)s00 domains within the temperature range of the phase coexistence. Remaining planar defects were observed within the Pnma phase at temperatures below the phase transition. From the analysis of high-resolution electron micrographs, these defects were proven to be antiphase boundaries with a displacement vector of R=1/2 [111]. - High-temperature HRTEM (zone axis [010]) of a phase boundary between domains of the Pnma (lower left) and Imma(00g)s00 (upper right) structure. Micrograph recorded at 970 K. Corresponding FFT patterns are shown on the right.

• OSTI ID: 21370443
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 6 Vol. 182; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
COHERENT SCATTERING
COMPUTER CODES
CRYSTAL DEFECTS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
DIFFERENTIAL THERMAL ANALYSIS
DIFFRACTION
ELECTRON MICROSCOPY
HEATING
IRON COMPOUNDS
MICROSCOPY
MONOCRYSTALS
ORTHORHOMBIC LATTICES
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SCATTERING
SPACE GROUPS
SYMMETRY GROUPS
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
TETRAGONAL LATTICES
THERMAL ANALYSIS
TRANSITION ELEMENT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION