Synthesis and crystal structure of ABW-type SrFe1.40V0.60O4

Gstir, T.; Kahlenberg, V.; Krüger, H.; Penner, S.

doi:10.1107/S205698902000496X

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Volume 76| Part 5| May 2020| Pages 664-667

https://doi.org/10.1107/S205698902000496X

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Synthesis and crystal structure of ABW-type SrFe_1.40V_0.60O₄

Thomas Gstir,^a Volker Kahlenberg,^a ^* Hannes Krüger ^a and Simon Penner ^b

^aUniversity of Innsbruck, Institute of Mineralogy & Petrography, Innrain 52, A-6020 Innsbruck, Austria, and ^bUniversity of Innsbruck, Department of Physical Chemistry, Innrain 52c, A-6020 Innsbruck, Austria
^*Correspondence e-mail: volker.kahlenberg@uibk.ac.at

Edited by M. Weil, Vienna University of Technology, Austria (Received 30 March 2020; accepted 8 April 2020; online 17 April 2020)

Single crystals of SrFe_1.40V_0.60O₄, strontium tetraoxidodi[ferrate(III)/vanadate(III)], have been obtained as a side product in the course of sinter experiments aimed at the synthesis of double perovskites in the system SrO–Fe₂O₃–V₂O₅. The crystal structure can be characterized by layers of six-membered rings of TO₄-tetrahedra (T: Fe^III, V^III) perpendicular to [100]. Stacking of the layers along [100] results in a three-dimensional framework enclosing tunnel-like cavities in which Sr^II cations are incorporated for charge compensation. The sequence of directedness of up (U) and down (D) pointing vertices of neighboring tetrahedra in a single six-membered ring is UUUDDD. The topology of the tetrahedral framework belongs to the zeolite-type ABW.

Keywords: crystal structure; cation substitution; solid solution; topology; zeolite; ABW.

CCDC reference: 1995764

1. Chemical context

Solid oxide fuel cell (SOFC) technology is considered as particularly promising for energy storage applications (Larminie et al., 2003 ). SOFCs are electrochemical devices that consist of three main parts: (i) a redox-capable porous cathode that reduces O₂ to O^2– anions, (ii) an electrolyte transporting these anions to the anode, and (iii) the anode, where the fuel (hydrogen or carbon-containing fuels) is electro-oxidized by the O^2– anions to CO₂ and H₂O (Huang & Goodenough, 2009 ). Double perovskites with the general composition A₂(BB′)O₆ have been studied intensively as potential anode materials in SOFCs (Xu et al., 2019 ). In the course of an explorative study on double perovskites combining mixed ionic-electronic conductivity with catalytic activity for fuel oxidation, we tried to synthesize Sr₂FeVO₆ using a ceramic synthesis route in the range between 1473 and 1573 K. For the highest reaction temperature, where partial melting occurred, a member of the previously unknown SrFe_xV_2–xO₄ solid-solution series was observed as a side-product, and the crystal structure of the member with x = 1.40 is reported here.

2. Structural commentary

SrFe_1.40V_0.60O₄ exhibits a three-dimensional framework of corner-linked TO₄-tetrahedra (T: Fe^III, V^III). Charge compensation is achieved by the incorporation of Sr^II cations residing in tunnel-like cavities running parallel to [100] (Fig. 1). The compound is isostructural with SrFe₂O₄ (Kahlenberg & Fischer, 2001 ) and γ-SrGa₂O₄ (Kahlenberg et al., 2000 ).

Figure 1
Projection of the framework structure along [100]. [TO₄] tetrahedra are shown in blue. Oxygen and strontium atoms are given in red and orange, respectively. Displacement ellipsoids are drawn at the 70% probability level.

All atoms occupy general positions. Fe <—> V substitutions occur on each of the four symmetrically non-equivalent T-sites occupying the centers of distorted tetrahedra formed by oxygen atoms. Site-population refinements indicate no clear trend when comparing the individual Fe:V distributions. The Fe:V population at the T-sites is more or less balanced ranging from 64 (3) to 75 (3)% of iron. Individual T–-O distances adopt values between 1.820 (6) and 1.901 (5) Å. The distortion of the tetrahedra is also reflected in the variation of the O—T—O bond angles scattering between 98.2 (2) and 129.9 (2)°. According to Robinson et al. (1971 ), the distortions can be expressed numerically by means of the quadratic elongation λ and the angle variance σ². These two parameters exhibit values between 1.009 and 1.016 for λ and 34.72 and 59.96 for σ².

Each of the two symmetrically independent Sr^II cations is coordinated by seven oxygen atoms within the channels of the framework. They are located off-center and have irregular coordination spheres formed by the oxygen atoms of two adjacent six-membered tetrahedral rings (Figs. 2, 3). Bond-valence-sum calculations using the parameter sets for the Sr—O bonds given by Brown & Altermatt (1985 ) resulted in the following values (in v.u.) considering cation–anion interactions up to 3.2 Å: Sr1: 1.911 and Sr2: 1.692. The considerable underbonding of the Sr2 position indicates that the bonds are stretched and that this Sr site resides in a cavity that is too large. A similar situation has been observed in isostructural SrFe₂O₄ and γ-SrGa₂O₄.

Figure 2
Representation of the coordination polyhedron around Sr1. Displacement ellipsoids are drawn at the 70% probability level. [Symmetry codes: (i) 1 − x, 1 − y, 1 − z; (ii) $[{1\over 2}]$ + x, $[{1\over 2}]$ − y, − $[{1\over 2}]$ + z; (iii) $[{3\over 2}]$ − x, $[{1\over 2}]$ + y, $[{1\over 2}]$ − z; (iv) − $[{1\over 2}]$ + x, $[{1\over 2}]$ − y, − $[{1\over 2}]$ + z].

Figure 3
Representation of the coordination polyhedron around Sr2. Ellipsoids are drawn at the 70% level. [Symmetry codes: (i) $[{3\over 2}]$ − x, $[{1\over 2}]$ + y, $[{1\over 2}]$ − z; (ii) $[{1\over 2}]$ − x, $[{1\over 2}]$ + y, $[{1\over 2}]$ − z; (iii) $[{1\over 2}]$ + x, $[{3\over 2}]$ − y, − $[{1\over 2}]$ + z; (iv) 1 − x, 1 − y, 1 − z; (v) x, 1 + y, z]

3. Topological features

SrFe_1.40V_0.60O₄ belongs to the ABW zeolite structure type (Baerlocher et al., 2007 ). This class of materials comprises a large number of representatives and has been investigated in great detail because of the complex phase transitions and interesting ferroic effects (Bu et al., 1997 ). The polyhedral connectivity results in a three-dimensional network built from six-, four- and eight-membered rings. Perpendicular to [100], for example, the structure can be decomposed into layers consisting of six-membered rings (S6R) of [TO₄]-tetrahedra forming honeycomb nets (Fig. 4). Within a single S6R, three tetrahedra with vertices up (U) alternate with three tetrahedra having their vertices down (D) (sequence of directedness: UUUDDD). Using the terminology of Flörke (1967 ), the relative orientation of paired tetrahedra belonging to different adjacent layers can be approximately classified as a trans-configuration (Fig. 1). Alternatively, the layers can be regarded as being constructed from the condensation of unbranched vierer single-chains via common corners. Perpendicular to [010] the network contains strongly corrugated layers of S4R and S8R (Fig. 5). The S8Rs are highly elliptical. Subsequent layers are connected by bridging vertex oxygen atoms, forming eight-ring channels that propagate along [010]. The elliptical shape of the channels is also reflected in the high framework density (Brunner & Meyer, 1989 ), with a value of 20.0 tetrahedral atoms/1000 Å³.

Figure 4
Single tetrahedral layer with six-membered rings in a projection along [100]. T-sites in the centres of the tetrahedra are shown in blue. Displacement ellipsoids are drawn at the 70% probability level.

Figure 5
Strongly folded tetrahedral layer with four- and eight-membered rings in a projection along [010]. Displacement ellipsoids are drawn at the 70% probability level.

4. Synthesis and initial characterization

Single-crystals of SrFe_1.40V_0.60O₄ were obtained in the course of a series of synthesis experiments aimed at the preparation of a possible double perovskite phase with composition Sr₂FeVO₆. Therefore, mixtures of the dried starting materials SrCO₃, Fe₂O₃ and V₂O₅ were homogenized in the molar ratio 4:1:1 using a ball mill operated at 600 r.p.m. for 45 min under ethanol. The resulting slurry was dried for 24 h at 323 K and subsequently re-ground by hand. An amount of about 0.5 g was pressed into a pellet having a diameter of 12 mm. Thermal treatment was performed in a resistance-heated horizontal tube furnace in air. Therefore, the tablet was placed on a platinum foil contained in an alumina-ceramic combustion boat. The sample was heated from 298 K to 1473 K with a ramp of 100 K h⁻¹, followed by 25 K h⁻¹ to 1423 K and finally at 10 h K⁻¹ to 1573 K. After annealing for 48 h at the maximum temperature, the container was quenched to room temperature. The partially melted pellet was removed from the foil, crushed in an agate mortar and transferred to a glass slide under a reflected-light microscope. A first optical inspection revealed the presence of at least two different crystalline phases: (a) larger, transparent–colorless crystals up to 150 µm in size and (b) considerably smaller, opaque black–brown specimens with maximum dimensions of about 50 µm. Preliminary single-crystal diffraction experiments revealed the larger crystals to be Sr₃(VO₄)₂ (Carrillo-Cabrera & von Schnering, 1993 ) while the second phase could be indexed with a monoclinic primitive unit cell similar to the one reported for SrFe₂O₄ (Kahlenberg & Fischer, 2001). Since the larger samples of the second phase always exhibited intergrowth of several crystals, we finally decided to focus on the fraction with smaller crystallites and to perform the relevant diffraction studies for structure elucidation using synchrotron radiation at the X06DA beamline of the Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland. Therefore, a sample was mounted on the tip of a 0.25 mm diameter LithoLoop made by Molecular Dimensions Inc. with a drop of Paratone-N oil (Hampton Research) and flash cooled in a 100 K nitrogen gas stream.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. Initial coordinates for the refinement calculations were taken from the crystal structure refinement of SrFe₂O₄ (Kahlenberg & Fischer, 2001) after transformation to monoclinic second setting. Site-population refinements of the Fe:V ratios on the T-sites indicated the presence of a member of the solid-solution series SrFe_xV_2–xO₄.

Table 1
Experimental details

Crystal data
Chemical formula	SrFe_1.40V_0.60O₄
M_r	260.37
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	100
a, b, c (Å)	8.0594 (8), 10.8768 (9), 9.1218 (8)
β (°)	91.544 (7)
V (Å³)	799.33 (12)
Z	8
Radiation type	Synchrotron, λ = 0.72931 Å
μ (mm⁻¹)	20.91
Crystal size (mm)	0.03 × 0.02 × 0.01

Data collection
Diffractometer	Aerotech
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2018 $[Rigaku OD (2018). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]$ )
T_min, T_max	0.614, 0.871
No. of measured, independent and observed [I > 2σ(I)] reflections	5200, 1746, 1572
R_int	0.067
(sin θ/λ)_max (Å⁻¹)	0.641

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.050, 0.144, 1.14
No. of reflections	1746
No. of parameters	131
Δρ_max, Δρ_min (e Å⁻³)	1.74, −1.37
Computer programs: CrysAlis PRO (Rigaku OD, 2018 $[Rigaku OD (2018). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]$ ), SHELXL97 (Sheldrick, 2008 ), VESTA (Momma & Izumi, 2011 ), publCIF (Westrip, 2010 ) and WinGX (Farrugia, 2012 ).

Supporting information

CCDC reference: 1995764

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S205698902000496X/wm5552sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S205698902000496X/wm5552Isup2.hkl

checkCIF report

Computing details top

Data collection: CrysAlis PRO (Rigaku OD, 2018); cell refinement: CrysAlis PRO (Rigaku OD, 2018); data reduction: CrysAlis PRO (Rigaku OD, 2018); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: VESTA (Momma & Izumi, 2011); software used to prepare material for publication: publCIF (Westrip, 2010) and WinGX (Farrugia, 2012).

Strontium tetraoxidodi[ferrate(III)/vanadate(III)] top

Crystal data top

SrFe_1.40V_0.60O₄	F(000) = 961.6
M_r = 260.37	D_x = 4.327 Mg m⁻³
Monoclinic, P2₁/n	Synchrotron radiation, λ = 0.72931 Å
Hall symbol: -P 2yn	Cell parameters from 2398 reflections
a = 8.0594 (8) Å	θ = 3.5–33.9°
b = 10.8768 (9) Å	µ = 20.91 mm⁻¹
c = 9.1218 (8) Å	T = 100 K
β = 91.544 (7)°	Fragment, brown-black
V = 799.33 (12) Å³	0.03 × 0.02 × 0.01 mm
Z = 8

Data collection top

Aerotech diffractometer	1746 independent reflections
Radiation source: SLS super-bending magnet 2.9T, X06DA	1572 reflections with I > 2σ(I)
Bartels Monochromator with dual channel cut crystals (DCCM) in (±∓) geometry monochromator	R_int = 0.067
Detector resolution: 5.81 pixels mm^-1	θ_max = 27.9°, θ_min = 3.0°
rotation method scans	h = −9→10
Absorption correction: multi-scan (CrysAlis PRO; Rigaku OD, 2018)	k = −13→13
T_min = 0.614, T_max = 0.871	l = −11→11
5200 measured reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: isomorphous structure methods
R[F² > 2σ(F²)] = 0.050	Secondary atom site location: notdet
wR(F²) = 0.144	w = 1/[σ²(F_o²) + (0.0821P)²] where P = (F_o² + 2F_c²)/3
S = 1.14	(Δ/σ)_max < 0.001
1746 reflections	Δρ_max = 1.74 e Å⁻³
131 parameters	Δρ_min = −1.37 e Å⁻³

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > 2σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Sr1	0.49713 (9)	0.34684 (7)	0.20513 (7)	0.0190 (3)
Sr2	0.50716 (9)	0.89165 (6)	0.23511 (8)	0.0193 (3)
Fe1	0.22326 (15)	0.13896 (10)	0.06706 (12)	0.0163 (4)	0.64 (3)
Fe2	0.29893 (14)	0.13638 (10)	0.40844 (12)	0.0164 (4)	0.75 (3)
Fe3	0.17887 (15)	0.88717 (9)	0.93230 (12)	0.0166 (4)	0.71 (4)
Fe4	0.74301 (15)	0.11238 (9)	0.40681 (12)	0.0159 (4)	0.70 (3)
V1	0.22326 (15)	0.13896 (10)	0.06706 (12)	0.0163 (4)	0.36 (3)
V2	0.29893 (14)	0.13638 (10)	0.40844 (12)	0.0164 (4)	0.25 (3)
V3	0.17887 (15)	0.88717 (9)	0.93230 (12)	0.0166 (4)	0.29 (4)
V4	0.74301 (15)	0.11238 (9)	0.40681 (12)	0.0159 (4)	0.30 (3)
O1	0.0192 (7)	0.1337 (5)	0.9770 (6)	0.0218 (11)
O2	0.5181 (7)	0.1144 (5)	0.3576 (6)	0.0235 (12)
O3	0.2158 (6)	0.2238 (5)	0.2460 (5)	0.0208 (11)
O4	0.8217 (6)	0.0290 (5)	0.2457 (5)	0.0209 (11)
O5	0.8530 (6)	0.2590 (5)	0.4510 (5)	0.0196 (10)
O6	0.2367 (6)	0.7187 (5)	0.9126 (5)	0.0193 (11)
O7	0.7805 (7)	0.0230 (5)	0.5784 (5)	0.0238 (12)
O8	0.3105 (6)	0.9810 (5)	0.0607 (6)	0.0217 (11)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Sr1	0.0171 (4)	0.0186 (4)	0.0210 (4)	−0.0003 (3)	−0.0052 (3)	0.0001 (2)
Sr2	0.0184 (5)	0.0167 (4)	0.0226 (4)	0.0007 (2)	−0.0058 (3)	−0.0016 (2)
Fe1	0.0162 (7)	0.0141 (6)	0.0182 (6)	−0.0007 (4)	−0.0042 (4)	−0.0008 (4)
Fe2	0.0161 (7)	0.0146 (6)	0.0183 (6)	0.0005 (4)	−0.0038 (4)	0.0007 (4)
Fe3	0.0163 (7)	0.0148 (7)	0.0184 (6)	−0.0006 (4)	−0.0051 (4)	−0.0002 (4)
Fe4	0.0154 (7)	0.0140 (6)	0.0182 (6)	−0.0002 (4)	−0.0047 (4)	−0.0005 (4)
V1	0.0162 (7)	0.0141 (6)	0.0182 (6)	−0.0007 (4)	−0.0042 (4)	−0.0008 (4)
V2	0.0161 (7)	0.0146 (6)	0.0183 (6)	0.0005 (4)	−0.0038 (4)	0.0007 (4)
V3	0.0163 (7)	0.0148 (7)	0.0184 (6)	−0.0006 (4)	−0.0051 (4)	−0.0002 (4)
V4	0.0154 (7)	0.0140 (6)	0.0182 (6)	−0.0002 (4)	−0.0047 (4)	−0.0005 (4)
O1	0.024 (3)	0.022 (3)	0.019 (3)	−0.003 (2)	−0.002 (2)	−0.001 (2)
O2	0.024 (3)	0.020 (3)	0.027 (3)	0.002 (2)	−0.002 (2)	−0.004 (2)
O3	0.025 (3)	0.018 (3)	0.019 (2)	0.001 (2)	−0.0046 (19)	0.0019 (19)
O4	0.022 (3)	0.018 (3)	0.023 (2)	0.005 (2)	−0.003 (2)	0.002 (2)
O5	0.018 (3)	0.019 (2)	0.022 (2)	−0.001 (2)	−0.0044 (18)	0.001 (2)
O6	0.016 (3)	0.020 (3)	0.021 (2)	−0.002 (2)	−0.0041 (18)	0.0004 (19)
O7	0.031 (3)	0.018 (3)	0.022 (3)	−0.002 (2)	−0.009 (2)	0.0020 (19)
O8	0.021 (3)	0.015 (3)	0.028 (3)	0.000 (2)	−0.009 (2)	0.001 (2)

Geometric parameters (Å, º) top

Sr1—O1ⁱ	2.490 (5)	Fe4—O5	1.863 (5)
Sr1—O4ⁱⁱ	2.495 (5)	O1—V1^xiii	1.820 (6)
Sr1—O7ⁱⁱⁱ	2.506 (5)	O1—Fe1^xiii	1.820 (6)
Sr1—O6^iv	2.527 (5)	O1—V3^xii	1.832 (6)
Sr1—O3	2.668 (5)	O1—Fe3^xii	1.832 (6)
Sr1—O5ⁱⁱⁱ	2.811 (5)	O1—Sr1^xiv	2.490 (5)
Sr1—O2	2.889 (5)	O2—Sr2^ix	2.668 (5)
Sr2—O8	2.419 (5)	O3—Sr2^xv	2.571 (5)
Sr2—O5ⁱⁱ	2.517 (5)	O4—V3^iv	1.862 (5)
Sr2—O3^v	2.571 (5)	O4—Fe3^iv	1.862 (5)
Sr2—O2^vi	2.668 (5)	O4—Sr1^xvi	2.495 (5)
Sr2—O6^vii	2.706 (5)	O4—Sr2^ix	2.942 (5)
Sr2—O4^vi	2.942 (5)	O5—V1^xvii	1.872 (5)
Sr2—O7^iv	3.057 (6)	O5—Fe1^xvii	1.872 (5)
Fe1—O1^viii	1.820 (6)	O5—Sr2^xvi	2.517 (5)
Fe1—O8^ix	1.858 (5)	O5—Sr1^xvii	2.811 (5)
Fe1—O5ⁱⁱⁱ	1.872 (5)	O6—V2^xviii	1.891 (5)
Fe1—O3	1.877 (5)	O6—Fe2^xviii	1.891 (5)
Fe2—O7^x	1.853 (6)	O6—Sr1^iv	2.527 (5)
Fe2—O2	1.854 (6)	O6—Sr2^xix	2.706 (5)
Fe2—O3	1.869 (5)	O7—V2^x	1.853 (6)
Fe2—O6^xi	1.891 (5)	O7—Fe2^x	1.853 (6)
Fe3—O1^xii	1.832 (6)	O7—Sr1^xvii	2.506 (5)
Fe3—O4^iv	1.862 (5)	O7—Sr2^iv	3.057 (6)
Fe3—O8^xiii	1.863 (5)	O8—V1^vi	1.858 (5)
Fe3—O6	1.901 (5)	O8—Fe1^vi	1.858 (5)
Fe4—O4	1.853 (5)	O8—V3^viii	1.863 (5)
Fe4—O2	1.855 (6)	O8—Fe3^viii	1.863 (5)
Fe4—O7	1.860 (5)

O1ⁱ—Sr1—O4ⁱⁱ	74.21 (17)	V1^xiii—O1—Fe3^xii	126.0 (3)
O1ⁱ—Sr1—O7ⁱⁱⁱ	116.19 (18)	Fe1^xiii—O1—Fe3^xii	126.0 (3)
O4ⁱⁱ—Sr1—O7ⁱⁱⁱ	91.79 (17)	V3^xii—O1—Fe3^xii	0.00 (7)
O1ⁱ—Sr1—O6^iv	114.11 (17)	V1^xiii—O1—Sr1^xiv	119.1 (3)
O4ⁱⁱ—Sr1—O6^iv	78.52 (16)	Fe1^xiii—O1—Sr1^xiv	119.1 (3)
O7ⁱⁱⁱ—Sr1—O6^iv	123.51 (17)	V3^xii—O1—Sr1^xiv	114.9 (3)
O1ⁱ—Sr1—O3	86.65 (17)	Fe3^xii—O1—Sr1^xiv	114.9 (3)
O4ⁱⁱ—Sr1—O3	150.33 (16)	Fe2—O2—Fe4	150.7 (3)
O7ⁱⁱⁱ—Sr1—O3	76.34 (16)	Fe2—O2—Sr2^ix	101.6 (2)
O6^iv—Sr1—O3	130.71 (16)	Fe4—O2—Sr2^ix	96.4 (2)
O1ⁱ—Sr1—O5ⁱⁱⁱ	150.77 (17)	Fe2—O2—Sr1	87.9 (2)
O4ⁱⁱ—Sr1—O5ⁱⁱⁱ	134.45 (15)	Fe4—O2—Sr1	99.8 (2)
O7ⁱⁱⁱ—Sr1—O5ⁱⁱⁱ	65.40 (15)	Sr2^ix—O2—Sr1	126.3 (2)
O6^iv—Sr1—O5ⁱⁱⁱ	82.57 (15)	Fe2—O3—Fe1	114.8 (3)
O3—Sr1—O5ⁱⁱⁱ	64.90 (14)	Fe2—O3—Sr2^xv	123.0 (2)
O1ⁱ—Sr1—O2	66.00 (15)	Fe1—O3—Sr2^xv	116.5 (2)
O4ⁱⁱ—Sr1—O2	125.61 (16)	Fe2—O3—Sr1	94.5 (2)
O7ⁱⁱⁱ—Sr1—O2	138.40 (18)	Fe1—O3—Sr1	94.5 (2)
O6^iv—Sr1—O2	85.32 (17)	Sr2^xv—O3—Sr1	104.54 (18)
O3—Sr1—O2	62.13 (16)	Fe4—O4—V3^iv	117.3 (3)
O5ⁱⁱⁱ—Sr1—O2	93.22 (15)	Fe4—O4—Fe3^iv	117.3 (3)
O8—Sr2—O5ⁱⁱ	94.82 (17)	V3^iv—O4—Fe3^iv	0.00 (6)
O8—Sr2—O3^v	83.26 (16)	Fe4—O4—Sr1^xvi	117.2 (2)
O5ⁱⁱ—Sr2—O3^v	87.97 (16)	V3^iv—O4—Sr1^xvi	122.2 (2)
O8—Sr2—O2^vi	85.67 (18)	Fe3^iv—O4—Sr1^xvi	122.2 (2)
O5ⁱⁱ—Sr2—O2^vi	142.41 (18)	Fe4—O4—Sr2^ix	87.81 (19)
O3^v—Sr2—O2^vi	129.21 (18)	V3^iv—O4—Sr2^ix	103.8 (2)
O8—Sr2—O6^vii	175.50 (17)	Fe3^iv—O4—Sr2^ix	103.8 (2)
O5ⁱⁱ—Sr2—O6^vii	80.68 (15)	Sr1^xvi—O4—Sr2^ix	95.86 (17)
O3^v—Sr2—O6^vii	96.47 (15)	Fe4—O5—V1^xvii	111.1 (3)
O2^vi—Sr2—O6^vii	97.91 (16)	Fe4—O5—Fe1^xvii	111.1 (3)
O8—Sr2—O4^vi	111.49 (16)	V1^xvii—O5—Fe1^xvii	0.00 (8)
O5ⁱⁱ—Sr2—O4^vi	84.97 (15)	Fe4—O5—Sr2^xvi	124.3 (2)
O3^v—Sr2—O4^vi	164.10 (15)	V1^xvii—O5—Sr2^xvi	108.0 (2)
O2^vi—Sr2—O4^vi	60.41 (16)	Fe1^xvii—O5—Sr2^xvi	108.0 (2)
O6^vii—Sr2—O4^vi	68.34 (14)	Fe4—O5—Sr1^xvii	90.66 (18)
O8—Sr2—O7^iv	75.56 (16)	V1^xvii—O5—Sr1^xvii	90.07 (17)
O5ⁱⁱ—Sr2—O7^iv	155.43 (15)	Fe1^xvii—O5—Sr1^xvii	90.07 (17)
O3^v—Sr2—O7^iv	68.68 (15)	Sr2^xvi—O5—Sr1^xvii	127.46 (19)
O2^vi—Sr2—O7^iv	60.55 (17)	V2^xviii—O6—Fe2^xviii	0.00 (9)
O6^vii—Sr2—O7^iv	108.56 (14)	V2^xviii—O6—Fe3	109.4 (2)
O4^vi—Sr2—O7^iv	119.55 (14)	Fe2^xviii—O6—Fe3	109.4 (2)
O1^viii—Fe1—O8^ix	107.2 (2)	V2^xviii—O6—Sr1^iv	112.6 (2)
O1^viii—Fe1—O5ⁱⁱⁱ	106.0 (2)	Fe2^xviii—O6—Sr1^iv	112.6 (2)
O8^ix—Fe1—O5ⁱⁱⁱ	108.2 (2)	Fe3—O6—Sr1^iv	121.7 (2)
O1^viii—Fe1—O3	111.0 (2)	V2^xviii—O6—Sr2^xix	100.9 (2)
O8^ix—Fe1—O3	120.2 (2)	Fe2^xviii—O6—Sr2^xix	100.9 (2)
O5ⁱⁱⁱ—Fe1—O3	103.4 (2)	Fe3—O6—Sr2^xix	108.6 (2)
O7^x—Fe2—O2	103.2 (2)	Sr1^iv—O6—Sr2^xix	101.25 (16)
O7^x—Fe2—O3	114.2 (2)	V2^x—O7—Fe2^x	0.00 (7)
O2—Fe2—O3	101.0 (2)	V2^x—O7—Fe4	119.6 (3)
O7^x—Fe2—O6^xi	109.0 (2)	Fe2^x—O7—Fe4	119.6 (3)
O2—Fe2—O6^xi	116.4 (2)	V2^x—O7—Sr1^xvii	137.4 (2)
O3—Fe2—O6^xi	112.6 (2)	Fe2^x—O7—Sr1^xvii	137.4 (2)
O1^xii—Fe3—O4^iv	118.2 (2)	Fe4—O7—Sr1^xvii	100.9 (2)
O1^xii—Fe3—O8^xiii	105.8 (2)	V2^x—O7—Sr2^iv	88.8 (2)
O4^iv—Fe3—O8^xiii	105.6 (2)	Fe2^x—O7—Sr2^iv	88.8 (2)
O1^xii—Fe3—O6	98.2 (2)	Fe4—O7—Sr2^iv	101.6 (2)
O4^iv—Fe3—O6	112.6 (2)	Sr1^xvii—O7—Sr2^iv	95.81 (17)
O8^xiii—Fe3—O6	116.8 (2)	V1^vi—O8—Fe1^vi	0.00 (10)
O4—Fe4—O2	99.6 (2)	V1^vi—O8—V3^viii	108.4 (2)
O4—Fe4—O7	111.1 (2)	Fe1^vi—O8—V3^viii	108.4 (2)
O2—Fe4—O7	110.2 (3)	V1^vi—O8—Fe3^viii	108.4 (2)
O4—Fe4—O5	114.8 (2)	Fe1^vi—O8—Fe3^viii	108.4 (2)
O2—Fe4—O5	119.9 (2)	V3^viii—O8—Fe3^viii	0.00 (6)
O7—Fe4—O5	101.5 (2)	V1^vi—O8—Sr2	126.4 (2)
V1^xiii—O1—Fe1^xiii	0.00 (6)	Fe1^vi—O8—Sr2	126.4 (2)
V1^xiii—O1—V3^xii	126.0 (3)	V3^viii—O8—Sr2	123.1 (2)
Fe1^xiii—O1—V3^xii	126.0 (3)	Fe3^viii—O8—Sr2	123.1 (2)

Symmetry codes: (i) x+1/2, −y+1/2, z−1/2; (ii) −x+3/2, y+1/2, −z+1/2; (iii) x−1/2, −y+1/2, z−1/2; (iv) −x+1, −y+1, −z+1; (v) −x+1/2, y+1/2, −z+1/2; (vi) x, y+1, z; (vii) x+1/2, −y+3/2, z−1/2; (viii) x, y, z−1; (ix) x, y−1, z; (x) −x+1, −y, −z+1; (xi) −x+1/2, y−1/2, −z+3/2; (xii) −x, −y+1, −z+2; (xiii) x, y, z+1; (xiv) x−1/2, −y+1/2, z+1/2; (xv) −x+1/2, y−1/2, −z+1/2; (xvi) −x+3/2, y−1/2, −z+1/2; (xvii) x+1/2, −y+1/2, z+1/2; (xviii) −x+1/2, y+1/2, −z+3/2; (xix) x−1/2, −y+3/2, z+1/2.

Acknowledgements

Anuschka Pauluhn is thanked for her help during the data collections at the X06DA beamline. The research leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 730872, project CALIPSOplus.

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