Redetermination of EuScO₃

Single crystals of europium(III) scandate(III), with ideal formula EuScO₃, were grown from the melt using the micro-pulling-down method. The title compound crystallizes in an ortho­rhom­bic distorted perovskite-type structure, where Eu occupies the eightfold coordinated A sites (site symmetry m) and Sc resides on the centres of corner-sharing [ScO₆] octa­hedra (B sites with site symmetry ). The structure of EuScO₃ has been reported previously based on powder diffraction data [Liferovich & Mitchell (2004). J. Solid State Chem. 177, 2188–2197]. The results of the current redetermination based on single-crystal diffraction data shows an improvement in the precision of the structral and geometric parameters and reveals a defect-type structure. Site-occupancy refinements indicate an Eu deficiency on the A site coupled with O defects on one of the two O-atom positions. The crystallochemical formula of the investigated sample may thus be written as ^A(□_0.032Eu_0.968)^BScO_2.952.

Related literature

Details of the synthesis are described by Maier et al. (2007). Rietveld refinements on powders of LnScO₃ with Ln = La³⁺ to Ho³⁺ are reported by Liferovich & Mitchell (2004). The crystal structures of the Dy, Gd, Sm and Nd members refined from single-crystal diffraction data have been recently provided by Veličkov et al. (2007). The crystal structure of the isotypic TbScO₃ is described by Veličkov et al. (2008). Specific geometrical parameters have been calculated by means of the atomic coordinates following the concept of Zhao et al. (1993).

Experimental

Crystal data

• Eu_0.968ScO_2.952

• M_r = 239.24

• Orthorhombic, P n m a

• a = 5.7554 (7) Å

• b = 7.9487 (10) Å

• c = 5.5087 (6) Å

• V = 252.01 (5) ų

• Z = 4

• Mo Kα radiation

• μ = 26.28 mm⁻¹

• T = 293 (2) K

• 0.14 × 0.12 × 0.02 mm

Data collection

• Stoe IPDS-2 diffractometer

• Absorption correction: analytical (Alcock, 1970) T_min = 0.139, T_max = 0.397

• 2168 measured reflections

• 362 independent reflections

• 345 reflections with I > 2σ(I)

• R_int = 0.055

Refinement

• R[F² > 2σ(F²)] = 0.021

• wR(F²) = 0.051

• S = 1.27

• 362 reflections

• 31 parameters

• 1 restraint

• Δρ_max = 1.40 e Å⁻³

• Δρ_min = −0.84 e Å⁻³

Table 1
Selected bond lengths (Å)

Eu1—O1^i	2.276 (5)
Eu1—O2^ii	2.304 (3)
Eu1—O1^iii	2.375 (5)
Eu1—O2^iv	2.611 (3)
Eu1—O2^v	2.845 (3)
Sc2—O2^ii	2.094 (3)
Sc2—O2^vi	2.107 (3)
Sc2—O1^vii	2.1108 (16)
Symmetry codes: (i) ; (ii) -x, -y+1, -z+1; (iii) x, y, z-1; (iv) ; (v) x, y-1, z-1; (vi) ; (vii) .

Data collection: X-AREA (Stoe & Cie, 2006); cell refinement: X-AREA; data reduction: X-RED (Stoe & Cie, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS for Windows (Dowty, 2004); software used to prepare material for publication: SHELXL97.

Supporting information

S1. Comment

Liferovich & Mitchell (2004) studied the crystal structure of lanthanoid scandates, including EuScO₃, by Rietveld analysis from powder diffraction data. Crystallographic data of DyScO₃, GdScO₃, SmScO₃ and NdScO₃ obtained from single crystals were recently reported by Veličkov et al. (2007), and for TbScO₃ by Veličkov et al. (2008). Based on these results it was possible to resolve disagreements concerning some structural characteristics and their dependence on the Ln-substitution. Whereas Liferovich & Mitchell (2004) observed no obvious continuous evolution, Veličkov et al. (2007) were able to show that the geometry and the distortion of the sites are linearly coupled with the size of the lanthanoid in the series from DyScO₃ to NdScO₃. With the structural refinement based on diffraction data collected from single crystalline EuScO₃, the present results provide further data for this series.

The orthorhombic distorted perovskite structure for EuScO₃ (Fig. 1) is confirmed from our refinements. Whereas the lattice parameters for EuScO₃ compare well with the data of Liferovich & Mitchell (2004), the fractional atomic coordinates show deviations of up to 0.006, resulting in slightly different geometrical parameters. The A-site is occupied by Eu in an eightfold coordination and has an average bond length of ^[8]<A—O> = 2.521 Å with a polyhedral bond length distortion of ^AΔ₈ = 7.98×10^-3 (Δn = 1/n Σ{(r_i-r)/r²). The B-site shows bond lengths typical for octahedrally coordinated scandium (<B—O> = 2.104 Å) and is rather distorted with ^BΔ₆ = 0.015×10^-3 and a bond angle variance of δ = 2.61°. The tilting of the corner sharing octahedra calculated after Zhao et al. (1993) are θ = 19.70° in [110] and Ø = 12.66° in [001] directions. From our data we can establish linear trends for the crystallochemical parameters from DyScO₃ to NdScO₃ depending on the Ln-substitution.

Related literature

Details of the synthesis are described by Maier et al. (2007). Rietveld refinements on powders of LnScO₃ with Ln = La³⁺ to Ho³⁺ are reported by Liferovich & Mitchell (2004). The crystal structures of the Dy, Gd, Sm and Nd members refined from single-crystal diffraction data have been recently provided by Veličkov et al. (2007). The crystal structure of the isotypic TbScO₃ is described by Veličkov et al. (2008). Specific geometrical parameters have been calculated by means of the atomic coordinates following the concept of Zhao et al. (1993).

S2. Experimental

An EuScO₃ fiber was grown using a micro-pulling-down apparatus with induction heating (Maier et al., 2007). The starting material was prepared from 4 N Eu₂O₃ and Sc₂O₃ powders by grinding a total weight of 5 g in a plastic mortar and pressing the mixture into pellets. An 5 ml iridium crucible with 500 mg of the starting material was placed on an iridium after-heater and heated by the inductor coil of a 10 kW rf Generator. The crucible after-heater arrangement was surrounded by a zirconia fiber tube and a high-purity alumina tube for thermal insulation. The experiments were carried out in a vacuum-tight steel chamber. It was evacuated before each experiment to 5 x10^-3 mbar and filled with 5 N argon gas. Subsequently, a constant flow of about 900 ml/min was kept. During growth the height of the molten zone and consequently the diameter of the fiber (~1 mm) was carefully controlled by manually increasing or decreasing the rf-power. Several starting compositions with different Eu to Sc ratios were tested, resulting in the optimal batch with 47.5 mol% Eu₂O₃ and 52.5 mol% Sc₂O₃.

The grown single-crystal was colourless. A part of the single-crystal fiber was crushed and the irregular shaped fragments were screened using a polarizing light microscope to find a sample of good optical quality for the diffraction experiments.

S3. Refinement

Site occupation refinements indicated deviations from full occupancy on the Eu1 (A-site) and the O2 sites. For the final refinement cycle a constraint ensuring charge neutrality was included. The crystallochemical formula of the investigated sample can thus be written as ^A(□_0.032Eu_0.968)^BScO_2.952. The highest peak and deepest hole of the difference Fourier map are located 0.84 Å and 1.42 Å away from the Eu1 position. In contrast to the previous Rietveld refinement, where the Pbnm setting of space group no. 62 was chosen, the standard setting Pnma was used for the present redetermination.

Computing details

Data collection: X-AREA (Stoe & Cie, 2006); cell refinement: X-AREA (Stoe & Cie, 2006); data reduction: X-RED (Stoe & Cie, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS for Windows (Dowty, 2004); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The orthorhombic perovskite structure of EuScO3 is characterized by a tilted corner sharing ScO6 framework incorporating the 8-fold coordinated Eu sites. The ScO6 octahedra are yellow, the Eu atoms are given in grey and the O atoms are presented in red.
	Fig. 2. Projection of the EuScO3 structure along [010], showing the Eu atoms and the Sc coordination with displacement ellipsoids at the 80% probability level.

europium(III) scandate(III)

Crystal data

Eu0.968ScO2.952	F(000) = 422.4
Mr = 239.24	Dx = 6.307 Mg m^−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2n	Cell parameters from 2218 reflections
a = 5.7554 (7) Å	θ = 2.6–29.2°
b = 7.9487 (10) Å	µ = 26.28 mm^−1
c = 5.5087 (6) Å	T = 293 K
V = 252.01 (5) Å^3	Platy fragment, colourless
Z = 4	0.14 × 0.12 × 0.02 mm

Data collection

Stoe IPDS-2 diffractometer	362 independent reflections
Radiation source: fine-focus sealed tube	345 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.055
Detector resolution: 6.67 pixels mm^-1	θmax = 29.1°, θmin = 4.5°
ω scans	h = −7→7
Absorption correction: analytical (Alcock, 1970)	k = −10→9
Tmin = 0.139, Tmax = 0.397	l = −7→7
2168 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.021	w = 1/[σ^2(Fo^2) + (0.0211P)^2 + 0.9412P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.051	(Δ/σ)max = 0.011
S = 1.27	Δρmax = 1.40 e Å^−3
362 reflections	Δρmin = −0.84 e Å^−3
31 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
1 restraint	Extinction coefficient: 0.113 (5)

Special details

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Eu1	0.05854 (5)	0.25	0.01589 (6)	0.0090 (2)	0.9677 (13)
Sc2	0	0	0.5	0.0078 (3)
O1	0.4506 (8)	0.25	0.8815 (9)	0.0111 (9)
O2	0.1954 (6)	0.9378 (4)	0.8078 (6)	0.0112 (7)	0.9758 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Eu1	0.0070 (3)	0.0102 (3)	0.0098 (3)	0	0.00051 (11)	0
Sc2	0.0064 (6)	0.0079 (6)	0.0090 (6)	0.0006 (6)	0.0000 (3)	0.0000 (3)
O1	0.011 (2)	0.008 (2)	0.014 (2)	0	−0.0025 (17)	0
O2	0.0096 (16)	0.0121 (17)	0.0119 (14)	−0.0019 (12)	−0.0018 (11)	0.0005 (12)

Geometric parameters (Å, º)

Eu1—O1^i	2.276 (5)	Sc2—O2^ii	2.094 (3)
Eu1—O2^ii	2.304 (3)	Sc2—O2^xii	2.094 (3)
Eu1—O2^iii	2.304 (3)	Sc2—O2^vi	2.107 (3)
Eu1—O1^iv	2.375 (5)	Sc2—O2^xiii	2.107 (3)
Eu1—O2^v	2.611 (3)	Sc2—O1^xiv	2.1108 (16)
Eu1—O2^vi	2.611 (3)	Sc2—O1^x	2.1108 (16)
Eu1—O2^vii	2.845 (3)	Sc2—Eu1^xv	3.2268 (4)
Eu1—O2^viii	2.845 (3)	Sc2—Eu1^i	3.2268 (4)
Eu1—Sc2^ix	3.2268 (4)	Sc2—Eu1^xvi	3.3428 (4)
Eu1—Sc2^x	3.2268 (4)	Sc2—Eu1^xvii	3.4841 (4)
Eu1—Sc2^xi	3.3428 (4)	Sc2—Eu1^xviii	3.4841 (4)
Eu1—Sc2	3.3428 (4)
O1^i—Eu1—O2^ii	103.43 (12)	O2^xii—Sc2—O2^vi	90.88 (6)
O1^i—Eu1—O2^iii	103.43 (12)	O2^ii—Sc2—O2^xiii	90.88 (6)
O2^ii—Eu1—O2^iii	80.77 (17)	O2^xii—Sc2—O2^xiii	89.12 (6)
O1^i—Eu1—O1^iv	87.69 (11)	O2^vi—Sc2—O2^xiii	180
O2^ii—Eu1—O1^iv	137.24 (9)	O2^ii—Sc2—O1^xiv	87.46 (16)
O2^iii—Eu1—O1^iv	137.24 (9)	O2^xii—Sc2—O1^xiv	92.54 (16)
O1^i—Eu1—O2^v	137.77 (9)	O2^vi—Sc2—O1^xiv	92.67 (15)
O2^ii—Eu1—O2^v	117.06 (6)	O2^xiii—Sc2—O1^xiv	87.33 (15)
O2^iii—Eu1—O2^v	73.38 (8)	O2^ii—Sc2—O1^x	92.54 (16)
O1^iv—Eu1—O2^v	71.14 (12)	O2^xii—Sc2—O1^x	87.46 (16)
O1^i—Eu1—O2^vi	137.77 (9)	O2^vi—Sc2—O1^x	87.33 (15)
O2^ii—Eu1—O2^vi	73.38 (8)	O2^xiii—Sc2—O1^x	92.67 (15)
O2^iii—Eu1—O2^vi	117.06 (6)	O1^xiv—Sc2—O1^x	180
O1^iv—Eu1—O2^vi	71.14 (12)	Sc2^xix—O1—Sc2^xv	140.6 (2)
O2^v—Eu1—O2^vi	69.74 (15)	Sc2^xix—O1—Eu1^xx	105.10 (13)
O1^i—Eu1—O2^vii	71.82 (8)	Sc2^xv—O1—Eu1^xx	105.10 (13)
O2^ii—Eu1—O2^vii	77.31 (12)	Sc2^xix—O1—Eu1^xviii	91.82 (14)
O2^iii—Eu1—O2^vii	155.61 (9)	Sc2^xv—O1—Eu1^xviii	91.82 (14)
O1^iv—Eu1—O2^vii	67.12 (8)	Eu1^xx—O1—Eu1^xviii	124.0 (2)
O2^v—Eu1—O2^vii	126.63 (6)	Sc2^xxi—O2—Sc2^xxii	143.00 (18)
O2^vi—Eu1—O2^vii	66.38 (5)	Sc2^xxi—O2—Eu1^ii	98.83 (13)
O1^i—Eu1—O2^viii	71.82 (8)	Sc2^xxii—O2—Eu1^ii	117.90 (14)
O2^ii—Eu1—O2^viii	155.61 (9)	Sc2^xxi—O2—Eu1^xxii	85.85 (11)
O2^iii—Eu1—O2^viii	77.31 (12)	Sc2^xxii—O2—Eu1^xxii	89.57 (12)
O1^iv—Eu1—O2^viii	67.12 (8)	Eu1^ii—O2—Eu1^xxii	103.48 (13)
O2^v—Eu1—O2^viii	66.38 (5)	Sc2^xxi—O2—Eu1^xxiii	88.37 (12)
O2^vi—Eu1—O2^viii	126.63 (6)	Sc2^xxii—O2—Eu1^xxiii	79.82 (10)
O2^vii—Eu1—O2^viii	121.45 (13)	Eu1^ii—O2—Eu1^xxiii	102.69 (12)
O2^ii—Sc2—O2^xii	180	Eu1^xxii—O2—Eu1^xxiii	153.77 (14)
O2^ii—Sc2—O2^vi	89.12 (6)

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