Valence state of europium and samarium in Ln2Hf2O7 (Ln = Eu, Sm) based oxygen ion conductors

A. V. Shlyakhtina; N. V. Lyskov; A. N. Shchegolikhin; I. V. Kolbanev; S. A. Chernyak; E. Yu Konysheva

doi:10.1016/j.ceramint.2021.06.099

Valence state of europium and samarium in Ln₂Hf₂O₇ (Ln = Eu, Sm) based oxygen ion conductors

A. V. Shlyakhtina, N. V. Lyskov, A. N. Shchegolikhin, I. V. Kolbanev, S. A. Chernyak, E. Yu Konysheva

Department of Chemical and Environmental Engineering

Research output: Journal Publication › Article › peer-review

9 Citations (Scopus)

Abstract

Ln₂(Hf_2-xLn_x)O_7-x/2 (Ln = Sm, Eu; x = 0.1) pyrochlores have been prepared via mechanical activation of oxide mixtures, followed by heat treatment for 4h at 1450 and 1600 °C, respectively. According to the ESR data, the Eu cations on the Hf site in the Hf_1-xEu_xO₆ octahedra in pyrochlore Eu₂(Hf_2-xEu_x)O_7-x/2 (x = 0.1) are most readily oxidized and reduced. Oxidation at 840 °C for 24h in air reduces the total conductivity of the Ln₂(Hf_2-xLn_x)O_7-x/2 (Ln = Sm, Eu; x = 0.1) by a factor of 2.5–6, due to the decrease in the concentrations of oxygen vacancies and Ln²⁺ ions as a result of the oxidation. The anomalous low-frequency behavior of the permittivity of the Eu₂(Hf_2-xEu_x)O_7-x/2 (x = 0.1) at ~800 °C can be understood in terms of the changes in the oxygen sublattice of the pyrochlore structure as a result of the oxidation of divalent europium and partial filling of oxygen vacancies at this temperature.

Original language	English
Pages (from-to)	26898-26906
Number of pages	9
Journal	Ceramics International
Volume	47
Issue number	19
DOIs	https://doi.org/10.1016/j.ceramint.2021.06.099
Publication status	Published - 1 Oct 2021

Keywords

Electron spin resonance spectroscopy
Eu2Hf2O7
Oxygen-ion conductivity
Permittivity
Pyrochlore
Raman spectroscopy
Sm2Hf2O7
XRD

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10.1016/j.ceramint.2021.06.099

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title = "Valence state of europium and samarium in Ln2Hf2O7 (Ln = Eu, Sm) based oxygen ion conductors",

abstract = "Ln2(Hf2-xLnx)O7-x/2 (Ln = Sm, Eu; x = 0.1) pyrochlores have been prepared via mechanical activation of oxide mixtures, followed by heat treatment for 4h at 1450 and 1600 °C, respectively. According to the ESR data, the Eu cations on the Hf site in the Hf1-xEuxO6 octahedra in pyrochlore Eu2(Hf2-xEux)O7-x/2 (x = 0.1) are most readily oxidized and reduced. Oxidation at 840 °C for 24h in air reduces the total conductivity of the Ln2(Hf2-xLnx)O7-x/2 (Ln = Sm, Eu; x = 0.1) by a factor of 2.5–6, due to the decrease in the concentrations of oxygen vacancies and Ln2+ ions as a result of the oxidation. The anomalous low-frequency behavior of the permittivity of the Eu2(Hf2-xEux)O7-x/2 (x = 0.1) at ~800 °C can be understood in terms of the changes in the oxygen sublattice of the pyrochlore structure as a result of the oxidation of divalent europium and partial filling of oxygen vacancies at this temperature.",

keywords = "Electron spin resonance spectroscopy, Eu2Hf2O7, Oxygen-ion conductivity, Permittivity, Pyrochlore, Raman spectroscopy, Sm2Hf2O7, XRD",

author = "Shlyakhtina, {A. V.} and Lyskov, {N. V.} and Shchegolikhin, {A. N.} and Kolbanev, {I. V.} and Chernyak, {S. A.} and Konysheva, {E. Yu}",

note = "Publisher Copyright: {\textcopyright} 2021 Elsevier Ltd and Techna Group S.r.l.",

year = "2021",

month = oct,

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doi = "10.1016/j.ceramint.2021.06.099",

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T1 - Valence state of europium and samarium in Ln2Hf2O7 (Ln = Eu, Sm) based oxygen ion conductors

AU - Shlyakhtina, A. V.

AU - Lyskov, N. V.

AU - Shchegolikhin, A. N.

AU - Kolbanev, I. V.

AU - Chernyak, S. A.

AU - Konysheva, E. Yu

PY - 2021/10/1

Y1 - 2021/10/1

N2 - Ln2(Hf2-xLnx)O7-x/2 (Ln = Sm, Eu; x = 0.1) pyrochlores have been prepared via mechanical activation of oxide mixtures, followed by heat treatment for 4h at 1450 and 1600 °C, respectively. According to the ESR data, the Eu cations on the Hf site in the Hf1-xEuxO6 octahedra in pyrochlore Eu2(Hf2-xEux)O7-x/2 (x = 0.1) are most readily oxidized and reduced. Oxidation at 840 °C for 24h in air reduces the total conductivity of the Ln2(Hf2-xLnx)O7-x/2 (Ln = Sm, Eu; x = 0.1) by a factor of 2.5–6, due to the decrease in the concentrations of oxygen vacancies and Ln2+ ions as a result of the oxidation. The anomalous low-frequency behavior of the permittivity of the Eu2(Hf2-xEux)O7-x/2 (x = 0.1) at ~800 °C can be understood in terms of the changes in the oxygen sublattice of the pyrochlore structure as a result of the oxidation of divalent europium and partial filling of oxygen vacancies at this temperature.

AB - Ln2(Hf2-xLnx)O7-x/2 (Ln = Sm, Eu; x = 0.1) pyrochlores have been prepared via mechanical activation of oxide mixtures, followed by heat treatment for 4h at 1450 and 1600 °C, respectively. According to the ESR data, the Eu cations on the Hf site in the Hf1-xEuxO6 octahedra in pyrochlore Eu2(Hf2-xEux)O7-x/2 (x = 0.1) are most readily oxidized and reduced. Oxidation at 840 °C for 24h in air reduces the total conductivity of the Ln2(Hf2-xLnx)O7-x/2 (Ln = Sm, Eu; x = 0.1) by a factor of 2.5–6, due to the decrease in the concentrations of oxygen vacancies and Ln2+ ions as a result of the oxidation. The anomalous low-frequency behavior of the permittivity of the Eu2(Hf2-xEux)O7-x/2 (x = 0.1) at ~800 °C can be understood in terms of the changes in the oxygen sublattice of the pyrochlore structure as a result of the oxidation of divalent europium and partial filling of oxygen vacancies at this temperature.

KW - Electron spin resonance spectroscopy

KW - Eu2Hf2O7

KW - Oxygen-ion conductivity

KW - Permittivity

KW - Pyrochlore

KW - Raman spectroscopy

KW - Sm2Hf2O7

KW - XRD

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AN - SCOPUS:85108528416

SN - 0272-8842

VL - 47

SP - 26898

EP - 26906

JO - Ceramics International

JF - Ceramics International

IS - 19

ER -

Valence state of europium and samarium in Ln₂Hf₂O₇ (Ln = Eu, Sm) based oxygen ion conductors

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Keywords

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