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Title: Brownmillerite Ca 2 Co 2 O 5 : Synthesis, Stability, and Re-entrant Single Crystal to Single Crystal Structural Transitions

Abstract

We synthesized Ca 2Co 2O 5 in the brownmillerite form using a high-pressure optical-image floating zone furnace, and single crystals with dimensions up to 1.4×0.8×0.5 mm 3 were obtained. At room temperature, Ca 2Co 2O 5 crystallizes as a fully ordered brownmillerite variant in the orthorhombic space group Pcmb (No. 57) with unit cell parameters a=5.28960(10) Å, b=14.9240(2) Å, and c=10.9547(2) Å. Furthermore, with decreasing temperature, it undergoes re-entrant sequence of first-order structural phase transitions (Pcmb→ P2/c11→ P121/m1→ Pcmb) that is unprecedented among brownmillerites, broadening the family of space groups available to these materials and challenging current approaches for sorting the myriad variants of brownmillerite structures. Magnetic susceptibility data indicate antiferromagnetic ordering in Ca 2Co 2O 5 occurs near 240 K, corroborated by neutron powder diffraction. Below 140 K, Ca 2Co 2O 5 shows a weak ferromagnetic component directed primarily along the b axis, and it also exhibits thermal and magnetic history dependence in magnetization.

Authors:
 [1];  [1];  [1];  [1];  [2];  [1];  [3];  [1]
  1. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
  2. Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Division
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division; Univ. of Chicago, IL (United States). The James Franck Inst. and Dept. of Physics
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1355783
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 26; Journal Issue: 24; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Zhang, Junjie, Zheng, Hong, Malliakas, Christos D., Allred, Jared M., Ren, Yang, Li, Qing’an, Han, Tian-Heng, and Mitchell, J. F. Brownmillerite Ca 2 Co 2 O 5 : Synthesis, Stability, and Re-entrant Single Crystal to Single Crystal Structural Transitions. United States: N. p., 2014. Web. doi:10.1021/cm503873x.
Zhang, Junjie, Zheng, Hong, Malliakas, Christos D., Allred, Jared M., Ren, Yang, Li, Qing’an, Han, Tian-Heng, & Mitchell, J. F. Brownmillerite Ca 2 Co 2 O 5 : Synthesis, Stability, and Re-entrant Single Crystal to Single Crystal Structural Transitions. United States. doi:10.1021/cm503873x.
Zhang, Junjie, Zheng, Hong, Malliakas, Christos D., Allred, Jared M., Ren, Yang, Li, Qing’an, Han, Tian-Heng, and Mitchell, J. F. Thu . "Brownmillerite Ca 2 Co 2 O 5 : Synthesis, Stability, and Re-entrant Single Crystal to Single Crystal Structural Transitions". United States. doi:10.1021/cm503873x. https://www.osti.gov/servlets/purl/1355783.
@article{osti_1355783,
title = {Brownmillerite Ca 2 Co 2 O 5 : Synthesis, Stability, and Re-entrant Single Crystal to Single Crystal Structural Transitions},
author = {Zhang, Junjie and Zheng, Hong and Malliakas, Christos D. and Allred, Jared M. and Ren, Yang and Li, Qing’an and Han, Tian-Heng and Mitchell, J. F.},
abstractNote = {We synthesized Ca2Co2O5 in the brownmillerite form using a high-pressure optical-image floating zone furnace, and single crystals with dimensions up to 1.4×0.8×0.5 mm3 were obtained. At room temperature, Ca2Co2O5 crystallizes as a fully ordered brownmillerite variant in the orthorhombic space group Pcmb (No. 57) with unit cell parameters a=5.28960(10) Å, b=14.9240(2) Å, and c=10.9547(2) Å. Furthermore, with decreasing temperature, it undergoes re-entrant sequence of first-order structural phase transitions (Pcmb→ P2/c11→ P121/m1→ Pcmb) that is unprecedented among brownmillerites, broadening the family of space groups available to these materials and challenging current approaches for sorting the myriad variants of brownmillerite structures. Magnetic susceptibility data indicate antiferromagnetic ordering in Ca2Co2O5 occurs near 240 K, corroborated by neutron powder diffraction. Below 140 K, Ca2Co2O5 shows a weak ferromagnetic component directed primarily along the b axis, and it also exhibits thermal and magnetic history dependence in magnetization.},
doi = {10.1021/cm503873x},
journal = {Chemistry of Materials},
number = 24,
volume = 26,
place = {United States},
year = {2014},
month = {11}
}

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