1 / 9

Example 3.4: Ca 2 Fe 2 O 5

Example 3.4: Ca 2 Fe 2 O 5 HT structural phase transition, coexistence of two phases in single crystal with strong overlaps. Single crystal data measured with Stoe IPDS-II imaging plate system Input files: HT_phase.M40, HT_phase.m50, HT_phase.m90, HT_phase.m95 and LT_phase.cif.

takoda
Télécharger la présentation

Example 3.4: Ca 2 Fe 2 O 5

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Example 3.4: Ca2Fe2O5 HT structural phase transition, coexistence of two phases in single crystal with strong overlaps. Single crystal data measured with Stoe IPDS-II imaging plate system Input files: HT_phase.M40, HT_phase.m50, HT_phase.m90, HT_phase.m95 and LT_phase.cif. The example starts from solved phases and shows how to connect them Kruger, H., Kahlenberg, V., Petřiček, V., Phillipp, F., Wertl, W. (2009): “Hightemperature structural phase transition in Ca2Fe2O5 studied by in situ X-ray diffraction and transmission electron microscopy”. J. Solid State Chem. 182, 1515-1523

  2. Low temperature (LT) phase Symmetry Pnma, a = 5.4707Å , b = 14.9897Å, c = 5.6302Å High temperature (HT) phase (> 710 °C) Symmetry Imma(00γ)s00, a = 5.4707Å , b = 14.9897Å, c = 5.6302Å

  3. Indication of the phase transition LT → HT: • Reflections h+k+l= 2n should vanish, because HT phase has I centering • Satellite reflection should appear

  4. In broad region of temperatures (690-710°C) we see both reflections forbidden by I centering and satellites (reconstruction of reciprocal space) HT and LT phases coexist

  5. In broad region of temperatures (690-710°C) we see both reflections forbidden by I centering and satellites (Reconstruction of reciprocal space)

  6. Confirmation from HRTEM

  7. Opening the modulated structure HT • A lot of observed discarded reflections

  8. 2. Binding intervals of crenel functions q=(0,0,0) or (0,0,1) RRRRRR or LLLLLLL q=(0,0,0.5) RLRLRLRLRLRLR q=(0,0,0.595) 19% RR and LL pairs Fe2 and symmetry related Fe2#8 O3 and symmetry related O3#s8t-1,0,0 The crenel functions separate “left” and “right” configuration of Fe tetrahedron. They are either “left” or “right”, without 3d periodicity of alternation and without overlaps.

  9. 3. Adding LT phase Unit “twinning” matrix relates the phases No violations of systematic extinction:

More Related