4.7 Article

Tetragonal to cubic transition of Sr0.8Dy0.2CoO3-δ and oxygen mobility: TG-DSC-XRD study

Journal

JOURNAL OF ALLOYS AND COMPOUNDS
Volume 860, Issue -, Pages -

Publisher

ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2020.158257

Keywords

Ceramics; Perovskite; Phase transitions; Oxygen mobility; Thermal analysis; X-ray diffraction

Funding

  1. Russian Foundation for Basic Research, RFBR [19-03-00017]
  2. BRFBR [18-52-00017]
  3. Russian Foundation for Basic Research
  4. Government of Krasnoyarsk Territory
  5. Krasnoyarsk Regional Fund of Science [18-42-243004]
  6. [AAAA-A17-117021310222-4]

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Processes of ordering and disordering of Sr2+/Dy(3+) cations in a single-phase Sr0.8Dy0.2CoO3-delta were investigated using TG-DSC and XRD techniques. The characteristics of the ordered-disordered phase transition were found to be highly sensitive to the cooling rate.
Processes of ordering (d-o) and disordering (o-d) of Sr2+/Dy(3+ )cations in a single-phase Sr0.8Dy0.2CoO3-delta was investigated by TG-DSC and XRD as a function of heating/cooling rate (beta= 2,10,20,50,99 K min(-1) and similar to 50 K/s) in 20% O-2-Ar flow. According to DSC data the interconversion of disordered cubic (c) and ordered tetragonal (t) structure appears at 1276-1328 K as a first-order phase transition; the temperature and enthalpy of o-d transformation have only slight dependence on beta whereas the characteristics of reversed d-o process vary greatly with cooling rate. XRD powder patterns of all samples showed no indications of a simultaneous presence of c+t domains, pointing to a single phase composition (c or t). It was suggested that the observed behavior is a consequence of two simultaneous interconnected processes of A-sublattice melting and cation/ (anion vacancy) ordering. A rarely used novel TG-DSC method based on variable gas phase composition was utilized to study properties of mobile oxygen over Sr0.8Dy0.2CoO3-delta samples. It was shown that the appearance of tetragonal phase reduces both oxygen mobility and its bonding energy, the latter decreasing substantially only at high degree of Sr2+/Dy3+ ordering. (C) 2020 Elsevier B.V. All rights reserved.

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