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Title: New Mechanism for Ferroelectricity in the Perovskite Ca 2–x Mn x Ti 2 O 6 Synthesized by Spark Plasma Sintering

Perovskite oxides hosting ferroelectricity are particularly important materials for modern technologies. The ferroelectric transition in the well-known oxides BaTiO 3 and PbTiO 3 is realized by softening of a vibration mode in the cubic perovskite structure. For most perovskite oxides, octahedral-site tilting systems are developed to accommodate the bonding mismatch due to a geometric tolerance factor t = (A–O)/[√2(B–O)] < 1. In the absence of cations having lone-pair electrons, e.g., Bi 3+ and Pb 2+, all simple and complex A-site and B-site ordered perovskite oxides with a t < 1 show a variety of tilting systems, and none of them become ferroelectric. The ferroelectric CaMnTi 2O 6 oxide is, up to now, the only one that breaks this rule. It exhibits a columnar A-site ordering with a pronounced octahedral-site tilting and yet becomes ferroelectric at T c ≈ 650 K. Most importantly, the ferroelectricity at T < Tc is caused by an order–disorder transition instead of a displacive transition; this character may be useful to overcome the critical thickness problem experienced in all proper ferroelectrics. Application of this new ferroelectric material can greatly simplify the structure of microelectronic devices. However, CaMnTi2O6 is a high-pressure phase obtained at 7 GPa andmore » 1200 °C, which limits its application. Here we report a new method to synthesize a gram-level sample of ferroelectric Ca 2–xMn xTi 2O 6, having the same crystal structure as CaMnTi 2O 6 and a similarly high Curie temperature. The new finding paves the way for the mass production of this important ferroelectric oxide. In conclusion, we have used neutron powder diffraction to identify the origin of the peculiar ferroelectric transition in this double perovskite and to reveal the interplay between magnetic ordering and the ferroelectric displacement at low temperatures.« less
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  1. Univ. of Texas, Austin, TX (United States). Material Science and Engineering Program, Mechanical Engineering
  2. Univ. of Texas, Austin, TX (United States). Dept. of Physics
  3. Tokyo Univ. of Science, Chiba (Japan). Dept. of Pure and Applied Chemistry, Faculty of Science and Technology
  4. Gakushuin Univ., Tokyo (Japan). Dept. of Chemistry, Faculty of Science
  5. Spanish National Research Council (CSIC), Madrid (Spain). Inst. of Materials Science of Madrid
  6. Inst. Laue-Langevin (ILL),Grenoble (France)
  7. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division
  8. Univ. of Texas, Austin, TX (United States). Dept. of Chemistry
Publication Date:
Grant/Contract Number:
AC05-00OR22725; F-1066; F-1841; F-1038
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 140; Journal Issue: 6; Journal ID: ISSN 0002-7863
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
OSTI Identifier: