Nanodomain states of strontium ferrites and their structural - - PowerPoint PPT Presentation

Nanodomain states of strontium ferrites and their structural transformations

Uliana Ancharova (ISSCM SB RAS) Zakhar Vinokurov (BIC SB RAS) Svetlana Cherepanova (BIC SB RAS)

Synchrotron and Free electron laser Radiation: generation and application July 06 2016

SrFe1−yVyO2.5+x SrFe0.99V0.01O2.51 SrFe0.96V0.04O2.54

Sr(Fe1-yVy)O2.5+x Sr(Fe1-yMoy)O2.5+x Sr(Co0.8Fe0.2)O2.64 (Sr0.7La0.3)(Co0.5Al0.3Fe0.2)O2.54 Sr(Co0.75Nb0.05Fe0.2)O2.45 Sr(Co0.7Nb0.1Fe0.2)O2.47

SR, λ= 1.54Å

Strongly-non-stoichiometric perovskite-like oxides SrFeO3-δ

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SrFe0.95Mo0.05O2.5+x

[Lindberg F. et. al. // J. Solid State Chem. 2004. 177. 1592] Sr2Co2−xAlxO5 [Doorn R. H. E. et. al. // Solid State Ionics. 2000. 128. 65] La1−xSrxCoO3−δ [Liu Y. et al. // J. Solid State Chem. 2003. 170. 247] (Ba1−xLax)2In2O5+x [Nakayama N. et al. // J. Solid State Chem. 1987. 71. 403] SrFe1−xVxO2.5+x [Alario-Franco M.A. et al. // Materials Res. Bull. 1982. 17. 733] SrxNd1-xFeO3-y [D’Hondt H. et al. // J. Solid State Chem. 2009. 182. 356] Sr2Al0.78Mn1.22O5.2

SrFe0.92Mo0.8O2.5+x

Strongly-non-stoichiometric perovskite-like oxides SrFeO3-δ

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[McIntosh S. et al // Solid State Ionics. 2006. 177. 833.]

Sr(Co0.8Fe0.2)O3-δ

cracks

[Pei S. et al // Catalysis Letters. 1995. 30. 201.]

Nano-domain state at low pO2 improves mechanical stability of membranes

Arrenius plots for oxygen ion conductivity

[Markov A. et al. // Solid State Ionics. 2008. 179. 99.] [Markov A. et al // Solid State Ionics. 2008. 179. 1050.]

SrFe1−yMo6+

yO2.5+x

SrFe1−yW6+

yO2.5+x

y=0 y=0.1 y=0.05 y=0 y=0.1 y=0.2

• rthorhombic

cubic “order-disorder” phase transition: abrupt change in lattice volume

SrFeO3-δ

[Schmidt M. et al // J. Solid State Chem. 2001. 156. 292.]

• rthorhombic

cubic

Doping with high-charged cations leads to the formation of the system outside the homogeneity region of brownmillerite structure

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Structure investigations

To find correlations between configuration of nanodomain structure in strongly non-stoichiometric oxygen deficient oxides based in strontium ferrite SrFeO3-δ and accompanying them specific diffraction effects

[Takeda Y. et al. // J. Solid State Chem. 1986. 63. 237.]

+

• cation composition
• oxygen composition
• temperature
• different type of disordering
• diffraction effects of nanostructuring

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SrFe1-xMoxO3-δ SrFe1-xVxO3-δ

Weakly oxygen deficient SrFeO3-δ

Slow cooling at air Substitution with high charged cations: at normal conditions pO2 cubic perovskite structure remains V Mo λ=0.369Å λ=0.369Å Lattice parameter 3-δ ≈ 2.8-2.9

Strongly oxygen deficient SrFeO3-δ

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SrFe1-xVxO3-δ SrFe1-xMoxO3-δ Quenching in vacuum Substitution with high charged cations: during quenching at low pO2 cubic perovskite structure is not preserved V Mo <ε>≈0.2% <ε>≈0.6% <ε>≈1.0% <ε>≈1.2% <ε>≈0.8% <ε>≈0.5% <ε>≈0.4% <ε>≈0.2% <ε>≈0.3% <ε>≈0.5% <ε>≈1.0% <ε>≈0.7% <ε>≈0.4% <ε>≈0.3% λ=0.369Å λ=0.369Å Lattice parameters 3-δ ≈ 2.5-2.7

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V Mo SrFe1-xMxO3-δ Microdeformations Lattice parameters

Strongly oxygen deficient SrFeO3-δ

The reduced length of the unit cell along (141)BM plane l=

2 2 BM

(( / 4) ( / 2) ) / 2

BM

b d +

almost does not change, which means that twinning direction is the least stressful in bd plane. (141)BM=(110)Per

2D- diffraction I(2θ, χ)

2θ χ SrFe0.97Mo0.03O3-δ SrFe0.95Mo0.05O3-δ SrFe0.92Mo0.08O3-δ <ε>≈0.5-1% <ε>≈0.7-1.2% <ε>≈0.3-0.4% 1D nanodomain twinned 3D nanodomain stressed cluster not stressed

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Strongly oxygen deficient SrFeO3-δ

Nanodomain states according to HRTEM SrFe1-yMyO2.5+x (M=V,Mo)

0≤y≤0.03 0.04≤y≤0.1 <L>min=<D>max ≈ 20-40nm; <D>min ≈ 2-5nm L D

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Strongly oxygen deficient SrFeO3-δ

SrFe1-yMyO2.5+x (M=V,Mo)

(0.04≤y≤0.05) (0.06≤y≤0.1) states: monodomain

b b b b b b b b b b b ac ac + Increase in degree of disordering in the system

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Nanodomain states

Of strongly oxygen-deficient SrFeO3-δ depending on substitution degree of high-charged cations 1D nanodomain twinned 3D nanodomain stressed cluster not stressed (0≤y≤0.03) according to defect structure XRD simulation

y 1 2 3 12 (6)

Structure changes at heating to high temperatures

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Phase transitions of vacancy-ordered phases 2 3 1

ABO2.75 ABO2.875 ABO2.5 ABO3-δ ABO3-δ ABO3-δ

1 2 3

OПОП’ OТОТ’ ОOПООП’

SrFeO3-δ

[Takeda Y. et al. // J. Solid State

• Chem. - 1986. - 63. - P.237]

2 3 SrFeO3-δ

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Structure changes at heating to high temperatures

Evolution of superstructural reflections SrCo0.8Fe0.2O2.5+x x≈0.14

ABO2.5 ABO3-δ

λ= 0.369Å 3

+

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ABO2.75 ABO3-δ

2

OПОП’ SrFeO2.75+x x≈0.07

λ= 0.369Å 2

per per per

a c a b a a ≠ ≠ ≠ 2 ; 2 ; 2 2

• rthoperovskite

perovskite Nanodomain states of orthoperovskite

Structure changes at heating to high temperatures

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Domain structure of orthoperovskite

Influence on XRD

*

• Widths of superstructural reflections are

higher then for main

• Forms of peaks are symmetrical in despite of

low symmetry of orthoperovskite superstructure (ABO2.75) ABO3 8593 . 3 2 8436 . 3 2 8708 . 3 2 2 = = = c b a

0.017º λ= 0.369Å λ= 0.369Å

SrFeO2.82

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Domain structure of orthoperovskite at HRTEM

2 1 3 20nm

SrFeO2.82 obtained by slow cooling in air

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Structure changes at heating to high temperatures

In situ XRD investigations of quenching SrFeO3-δ in oxygen-deficient atmosphere

[Mizusaki J. et al. // J. Solid State Chem. 1992. 99. 166.]

95%N25%O2 99%N21%O2

• λ= 1.021Å

Thank you very much for your attention!

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