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(□0.032Eu0.968)BScO2.952.

Single crystals of europium(III) scandate(III), with ideal formula EuScO 3 , were grown from the melt using the micropulling-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 [ScO 6 ] octahedra (B sites with site symmetry 1). The structure of EuScO 3 has been reported previously based on powder diffraction data [Liferovich & Mitchell (2004). J. Solid State Chem. 177, 2188Chem. 177, -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 (& 0.032 Eu 0.968 ) B ScO 2.952 .

Related literature
Details of the synthesis are described by Maier et al. (2007). Rietveld refinements on powders of LnScO 3 with Ln = La 3+ to Ho 3+ 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 TbScO 3 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).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2214).

Redetermination of EuScO 3
V. Kahlenberg, D. Maier and B. Velickov Comment Liferovich & Mitchell (2004) studied the crystal structure of lanthanoid scandates, including EuScO 3 , by Rietveld analysis from powder diffraction data. Crystallographic data of DyScO 3 , GdScO 3 , SmScO 3 and NdScO 3 obtained from single crystals were recently reported by Veličkov et al. (2007), and for TbScO 3 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 DyScO 3 to NdScO 3 . With the structural refinement based on diffraction data collected from single crystalline EuScO 3 , the present results provide further data for this series.
The orthorhombic distorted perovskite structure for EuScO 3 (Fig. 1) is confirmed from our refinements. Whereas the lattice parameters for EuScO 3 compare well with the data of Liferovich & Mitchell (2004) From our data we can establish linear trends for the crystallochemical parameters from DyScO 3 to NdScO 3 depending on the Ln-substitution.

Experimental
An EuScO 3 fiber was grown using a micro-pulling-down apparatus with induction heating (Maier et al., 2007). The starting material was prepared from 4 N Eu 2 O 3 and Sc 2 O 3 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% Eu 2 O 3 and 52.5 mol% Sc 2 O 3 .
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.
supplementary materials sup-2 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 (□ 0.032 Eu 0.968 ) B ScO 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. Fig. 1. The orthorhombic perovskite structure of EuScO 3 is characterized by a tilted corner sharing ScO 6 framework incorporating the 8-fold coordinated Eu sites. The ScO 6 octahedra are yellow, the Eu atoms are given in grey and the O atoms are presented in red. Detector resolution: 6.67 pixels mm -1 θ max = 29.1º T = 293(2) K θ min = 4.5º ω scans h = −7→7 Absorption correction: analytical (Alcock, 1970) k = −10→9