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Effects of Nanodomains on Local and Long-Range Phase Transitions in Perovskite-Type Eu0.8Ca0.2TiO3–δ

Widenmeyer, Marc and Checchia, Stefano and Xiao, Xingxing and Scavini, Marco and Weidenkaff, Anke (2020):
Effects of Nanodomains on Local and Long-Range Phase Transitions in Perovskite-Type Eu0.8Ca0.2TiO3–δ.
In: Nanomaterials, 10 (4), p. 769. MDPI, ISSN 2079-4991,
DOI: 10.25534/tuprints-00013377,
[Article]

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 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.

Item Type: Article
Erschienen: 2020
Creators: Widenmeyer, Marc and Checchia, Stefano and Xiao, Xingxing and Scavini, Marco and Weidenkaff, Anke
Origin: Secondary publication via sponsored Golden Open Access
Title: Effects of Nanodomains on Local and Long-Range Phase Transitions in Perovskite-Type Eu0.8Ca0.2TiO3–δ
Language: English
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 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.

Journal or Publication Title: Nanomaterials
Journal volume: 10
Number: 4
Publisher: MDPI
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Materials and Resources
Date Deposited: 26 Aug 2020 13:41
DOI: 10.25534/tuprints-00013377
Official URL: https://doi.org/10.3390/nano10040769
URN: urn:nbn:de:tuda-tuprints-133772
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