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Effects of nanodomains on local and long-range phase transitions in perovskite-type Eu0.8Ca0.2TiO3–δ

Widenmeyer, Marc ; Checchia, Stefano LU orcid ; Xiao, Xingxing ; Scavini, Marco and Weidenkaff, Anke (2020) In Nanomaterials 10(4).
Abstract

The determination of reversible phase transitions in the perovskite-type thermoelectric oxide Eu0.8Ca0.2TiO3–δ is fundamental, since structural changes largely affect the thermal and electrical transport properties. The phase transitions were characterized by heat capacity measurements, Rietveld refinements, and pair distribution function (PDF) analysis of the diffraction data to achieve information on the phase transition temperatures and order as well as structural changes on the local level and the long range. On the long-range scale, Eu0.8Ca0.2TiO3–δ showed a phase transition sequence during heating from cubic at 100 < T < 592 K to tetragonal and finally back to... (More)

The determination of reversible phase transitions in the perovskite-type thermoelectric oxide Eu0.8Ca0.2TiO3–δ is fundamental, since structural changes largely affect the thermal and electrical transport properties. The phase transitions were characterized by heat capacity measurements, Rietveld refinements, and pair distribution function (PDF) analysis of the diffraction data to achieve information on the phase transition temperatures and order as well as structural changes on the local level and the long range. On the long-range scale, Eu0.8Ca0.2TiO3–δ showed a phase transition sequence during heating from cubic at 100 < T < 592 K to tetragonal and finally back to cubic at T > 846 K. The phase transition at T = 592 K (diffraction)/606 K (thermal analysis) was reversible with a very small thermal hysteresis of about 2 K. The local structure at 100 K was composed of a complex nanodomain arrangement of Amm2-and Pbnm-like local structures with different coherence lengths. Since in Eu0.8Ca0.2TiO3–δ the amount of Pbnm domains was too small to percolate, the competition of ferroelectrically distorted octahedra (Amm2 as in BaTiO3) and rigid, tilted octahedra (Pbnm as in CaTiO3) resulted in a cubic long-range structure at low temperatures.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Europium, Local structure, Oxide, Pair distribution function, Perovskite, Phase transitions, Rietveld refinements, Synchrotron diffraction, Titanium
in
Nanomaterials
volume
10
issue
4
article number
769
publisher
MDPI AG
external identifiers
  • scopus:85083729252
  • pmid:32316343
ISSN
2079-4991
DOI
10.3390/nano10040769
language
English
LU publication?
yes
id
1446c279-922d-44af-a973-16d7f3aee4a6
date added to LUP
2020-05-20 14:42:57
date last changed
2024-07-24 19:27:12
@article{1446c279-922d-44af-a973-16d7f3aee4a6,
  abstract     = {{<p>The determination of reversible phase transitions in the perovskite-type thermoelectric oxide Eu<sub>0.8</sub>Ca<sub>0.2</sub>TiO<sub>3–δ</sub> is fundamental, since structural changes largely affect the thermal and electrical transport properties. The phase transitions were characterized by heat capacity measurements, Rietveld refinements, and pair distribution function (PDF) analysis of the diffraction data to achieve information on the phase transition temperatures and order as well as structural changes on the local level and the long range. On the long-range scale, Eu<sub>0.8</sub>Ca<sub>0.2</sub>TiO<sub>3–δ</sub> showed a phase transition sequence during heating from cubic at 100 &lt; T &lt; 592 K to tetragonal and finally back to cubic at T &gt; 846 K. The phase transition at T = 592 K (diffraction)/606 K (thermal analysis) was reversible with a very small thermal hysteresis of about 2 K. The local structure at 100 K was composed of a complex nanodomain arrangement of Amm2-and Pbnm-like local structures with different coherence lengths. Since in Eu<sub>0.8</sub>Ca<sub>0.2</sub>TiO<sub>3–δ</sub> the amount of Pbnm domains was too small to percolate, the competition of ferroelectrically distorted octahedra (Amm2 as in BaTiO<sub>3</sub>) and rigid, tilted octahedra (Pbnm as in CaTiO<sub>3</sub>) resulted in a cubic long-range structure at low temperatures.</p>}},
  author       = {{Widenmeyer, Marc and Checchia, Stefano and Xiao, Xingxing and Scavini, Marco and Weidenkaff, Anke}},
  issn         = {{2079-4991}},
  keywords     = {{Europium; Local structure; Oxide; Pair distribution function; Perovskite; Phase transitions; Rietveld refinements; Synchrotron diffraction; Titanium}},
  language     = {{eng}},
  number       = {{4}},
  publisher    = {{MDPI AG}},
  series       = {{Nanomaterials}},
  title        = {{Effects of nanodomains on local and long-range phase transitions in perovskite-type Eu<sub>0.8</sub>Ca<sub>0.2</sub>TiO<sub>3–δ</sub>}},
  url          = {{http://dx.doi.org/10.3390/nano10040769}},
  doi          = {{10.3390/nano10040769}},
  volume       = {{10}},
  year         = {{2020}},
}