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

2 Strongly-non-stoichiometric perovskite-like oxides SrFeO 3- δ SrFe 1 − y V y O 2.5+ x SrFe 0.96 V 0.04 O 2.54 SrFe 0.99 V 0.01 O 2.51 SR, λ = 1.54Å Sr(Fe 1- y V y )O 2.5+ x Sr(Fe 1- y Mo y )O 2.5+ x Sr(Co 0.8 Fe 0.2 )O 2.64 (Sr 0.7 La 0.3 )(Co 0.5 Al 0.3 Fe 0.2 )O 2.54 Sr(Co 0.75 Nb 0.05 Fe 0.2 )O 2.45 Sr(Co 0.7 Nb 0.1 Fe 0.2 )O 2.47

3 Strongly-non-stoichiometric perovskite-like oxides SrFeO 3- δ SrFe 0.95 Mo 0.05 O 2.5+ x SrFe 0.92 Mo 0.8 O 2.5+ x [Lindberg F. et. al. // J. Solid State Chem. 2004. 177. 1592] Sr 2 Co 2 −x Al x O 5 [Doorn R. H. E. et. al. // Solid State Ionics. 2000. 128. 65] La 1 −x Sr x CoO 3 −δ [Liu Y. et al. // J. Solid State Chem. 2003. 170. 247] (Ba 1 −x La x ) 2 In 2 O 5+x [Nakayama N. et al. // J. Solid State Chem. 1987. 71. 403] SrFe 1 −x V x O 2.5+x [Alario-Franco M.A. et al. // Materials Res. Bull. 1982. 17. 733] Sr x Nd 1-x FeO 3-y [D’Hondt H. et al. // J. Solid State Chem. 2009. 182. 356] Sr 2 Al 0.78 Mn 1.22 O 5.2

4 Nano-domain state at low p O 2 improves mechanical stability of membranes Arrenius plots for oxygen ion conductivity “order-disorder” phase transition: abrupt change in lattice volume SrFe 1 − y Mo 6+ y O 2.5+ x orthorhombic cubic y =0.05 orthorhombic cubic y =0.1 y =0 Sr(Co 0.8 Fe 0.2 )O 3- δ SrFeO 3- δ [Markov A. et al // Solid State Ionics. 2008. 179. 1050.] [McIntosh S. et al // Solid State Ionics. 2006. 177. 833.] SrFe 1 − y W 6+ y O 2.5+ x [Schmidt M. et al // J. Solid State Chem. 2001. 156. 292.] y =0.1 cracks [Pei S. et al // Catalysis Letters. 1995. 30. 201.] y =0 Doping with high-charged cations leads to the y =0.2 formation of the system outside the homogeneity region of brownmillerite structure [Markov A. et al. // Solid State Ionics. 2008. 179. 99.]

5 Structure investigations To find correlations between configuration of nanodomain structure in strongly non-stoichiometric oxygen deficient oxides based in strontium ferrite SrFeO 3- δ and accompanying them specific diffraction effects + ● cation composition ● oxygen composition ● temperature ● different type of disordering ● diffraction effects of nanostructuring [Takeda Y. et al. // J. Solid State Chem. 1986. 63. 237.]

6 Weakly oxygen deficient SrFeO 3- δ λ =0.369Å SrFe 1- x V x O 3- δ Slow cooling at air 3- δ ≈ 2.8-2.9 Substitution with high charged cations: at normal conditions pO 2 cubic perovskite structure remains SrFe 1- x Mo x O 3- δ λ =0.369Å Lattice parameter V Mo

7 Strongly oxygen deficient SrFeO 3- δ λ =0.369Å SrFe 1- x V x O 3- δ Quenching in vacuum 3- δ ≈ 2.5-2.7 Substitution with high charged < ε > ≈ 0.3% cations: < ε > ≈ 0.4% during quenching at low p O 2 cubic < ε > ≈ 0.7% perovskite structure is not preserved < ε > ≈ 1.0% < ε > ≈ 0.5% λ =0.369Å SrFe 1- x Mo x O 3- δ < ε > ≈ 0.3% < ε > ≈ 0.2% < ε > ≈ 0.4% Lattice parameters < ε > ≈ 0.5% < ε > ≈ 0.8% < ε > ≈ 1.2% V < ε > ≈ 1.0% < ε > ≈ 0.6% Mo < ε > ≈ 0.2%

8 Strongly oxygen deficient SrFeO 3- δ SrFe 1- x M x O 3- δ V Mo Lattice parameters Microdeformations (141) BM =(110) Per The reduced length of the unit cell along (141) BM + plane l = 2 2 (( b / 4) ( d / 2) ) / 2 almost does not BM BM change, which means that twinning direction is the least stressful in bd plane.

9 Strongly oxygen deficient SrFeO 3- δ 2D- diffraction I (2 θ , χ ) χ 1D SrFe 0.97 Mo 0.03 O 3- δ nanodomain twinned < ε > ≈ 0.5-1% 3D SrFe 0.95 Mo 0.05 O 3- δ nanodomain stressed < ε > ≈ 0.7-1.2% SrFe 0.92 Mo 0.08 O 3- δ cluster not stressed < ε > ≈ 0.3-0.4% 2 θ

10 Strongly oxygen deficient SrFeO 3- δ Nanodomain states according to HRTEM ( M =V,Mo) SrFe 1- y M y O 2.5+ x D L 0 ≤ y ≤ 0.03 0.04 ≤ y ≤ 0.1 <L> min =<D> max ≈ 20-40nm; <D> min ≈ 2-5nm

11 Nanodomain states Of strongly oxygen-deficient SrFeO 3- δ depending on substitution degree of high-charged cations states: ( M =V,Mo) SrFe 1- y M y O 2.5+ x b 1 monodomain Increase in degree of disordering b 1D (0 ≤ y ≤ 0.03) in the system b nanodomain 2 twinned b 3D (0.04 ≤ y ≤ 0.05) b nanodomain 3 b stressed y ac b b cluster 12 (0.06 ≤ y ≤ 0.1) + b not stressed (6) ac b according to defect structure XRD simulation b

12 Structure changes at heating to high temperatures Phase transitions of vacancy-ordered phases [Takeda Y. et al. // J. Solid State SrFeO 3- δ Chem. - 1986. - 63. - P.237] 3 SrFeO 3- δ 2 1 O ПОП ’ O ТОТ ’ О O ПООП ’ AB O 2.875 AB O 2.75 AB O 2.5 1 2 3 AB O 3- δ AB O 3- δ AB O 3- δ 2 3

13 Structure changes at heating to high temperatures Evolution of superstructural reflections SrCo 0.8 Fe 0.2 O 2.5+ x x ≈ 0.14 + AB O 3- δ AB O 2.5 3 λ = 0.369Å

14 Structure changes at heating to high temperatures Nanodomain states of orthoperovskite SrFeO 2.75+ x x ≈ 0.07 a b c ≠ ≠ ≠ a ; a ; a per per per 2 2 2 2 2 orthoperovskite perovskite AB O 3- δ 2 AB O 2.75 O ПОП ’ λ = 0.369Å

15 Domain structure of orthoperovskite Influence on XRD SrFeO 2.82 a = 3 . 8708 2 2 b = 3 . 8436 2 AB O 3 c superstructure = 3 . 8593 2 (AB O 2.75 ) 0.017º * λ = 0.369Å ● Widths of superstructural reflections are higher then for main ● Forms of peaks are symmetrical in despite of λ = 0.369Å low symmetry of orthoperovskite

16 Domain structure of orthoperovskite at HRTEM SrFeO 2.82 obtained by slow cooling in air 1 2 3 20nm

17 Structure changes at heating to high temperatures In situ XRD investigations of quenching SrFeO 3- δ in oxygen-deficient atmosphere 95%N 2 5%O 2 • • λ = 1.021Å 99%N 2 1%O 2 [Mizusaki J. et al. // J. Solid State Chem. 1992. 99. 166.]

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