Received 5 June 2013
The title compound, Sr0.6Ba0.4Nb2O6 (strontium barium niobium oxide), belongs to the group of strontium-barium niobates with varying composition of Sr and Ba. Their general formula can be written as SrxBa1 - xNb2O6. Below the Curie temperature, Tc, these materials indicate ferroelectric properties. The Curie temperature for SBN60 is equal to 346±0.5 K so the structure is in the ferroelectric phase at the measurement temperature of 100 K. Characteristic for this family of compounds is the packing along the z-axis. The NbO6 corner-sharing octahedra surround three types of vacancy tunnels with pentagonal, square and triangular shapes. The Sr2+ ions partially occupy two unique sites, the first one located inside the pentagon and the second one in the square tunnels. Consequently, they are situated on the mirror plane and the intersection of two glide planes, respectively. The site inside the pentagonal tunnel is additionally disordered so that the same position is shared by Ba2+ and Sr2+ ions whereas another part of the Ba2+ ion occupies a different position (relative occupancies 0.43:0.41:0.16). One of the NbV atoms and three of the O2- ions occupy general positions. The second NbV atom is located on the intersection of the mirror planes. Two remaining O2- ions are located on the same mirror plane. Only the NbV atom and one of the O2- ions which is located on the mirror plane are not disordered. Each of the remaining O2- ions is split between two sites, with relative occupancies of 0.52:0.48 (O2- ions in general positions) and 0.64:0.36 (O2- ion on the mirror plane).
For detailed information about the growth of the crystals, see: Lukasiewicz et al. (2008). For their physical properties and possible applications in photorefractive, pyroelectric and electro-optic devices, see: Neurgaonkar et al. (1988); Chernaya et al. (2003); Megumi et al. (1976). For SBN61 crystals, a modulation in the structure was reported, see: Schefer et al. (2008); Woike et al. (2003). The structure of SBN61 has been determined from single crystal X-ray data; the structures of three other analogues (x = 34, 48, 82), with no disorder present, and the influence of temperature on their unit-cell parameters has been investigated with use of the powder data, see: Podlozhenov et al. (2006).
Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 1999); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FF2110 ).
The research for this paper was in part supported by the EU through the European Social Fund, contract No. UDA-POKL.04.01.01-00-072/09-00.
Agilent (2012). CrysAlis PRO. Agilent Technologies, Yarnton, England.
Brandenburg, K. & Putz, H. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany.
Chernaya, T. S., Volk, T. R., Maksimov, B. A., Blomberg, M. K., Ivleva, L. I., Verin, I. A. & Simonov, V. I. (2003). Cryst. Rep. 48, 933-938.
Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.
Lukasiewicz, T., Swirkowicz, M. A., Dec, J., Hofman, W. & Szyrski, W. (2008). J. Cryst. Growth, 310, 1464-1469.
Megumi, K., Nagatsuma, N., Ksashiwada, Y. & Furuhata, Y. (1976). J. Mater. Sci. 11, 1583-1592.
Neurgaonkar, R. R., Hall, W. F., Oliver, J. R., Ho, W. H. & Cory, W. K. (1988). Ferroelectrics, 87, 167-179.
Parsons, S. & Flack, H. (2004). Acta Cryst. A60, s61.
Podlozhenov, S., Graetsch, H. A., Schneider, J., Ulex, M., Wöhlecke, M. & Betzler, K. (2006). Acta Cryst. B62, 960-965.
Schefer, J., Schaniel, D., Petrícek, V., Woike, T., Cousson, A. & Woehlecke, M. (2008). Z. Kristallogr. 223, 399-407.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.
Woike, T., Petrícek, V., Dusek, M., Hansen, N. K., Fertey, P., Lecomte, C., Arakcheeva, A., Chapuis, G., Imlau, M. & Pankrath, R. (2003). Acta Cryst. B59, 28-35.