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Volume 69 
Part 1 
Page i1  
January 2013  

Received 8 November 2012
Accepted 28 November 2012
Online 5 December 2012

Key indicators
Powder Synchrotron study
T = 293 K
Mean [sigma](Si-O) = 0.020 Å
R = 0.052
wR = 0.073
Data-to-parameter ratio = 1.8
Details
Open access

Sr-fresnoite determined from synchrotron X-ray powder diffraction data

aHASYLAB/DESY, Notkestrasse 85, 22607 Hamburg, Germany, and bSchool of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, M13 9PL, England
Correspondence e-mail: tony.bell@desy.de

The fresnoite-type compound Sr2TiO(Si2O7), distrontium oxidotitanium disilicate, has been prepared by high-temperature solid-state synthesis. The results of a Rietveld refinement study, based on high-resolution synchrotron X-ray powder diffraction data, show that the title compound crystallizes in the space group P4bm and adopts the structure of other fresnoite-type mineral samples with general formula A2TiO(Si2O7) (A = alkaline earth metal cation). The structure consists of titanosilicate layers composed of corner-sharing SiO4 tetrahedra (forming Si2O7 disilicate units) and TiO5 square-based pyramids. These layers extend parallel to the ab plane and are stacked along the c axis. Layers of distorted SrO6 octahedra lie between the titanosilicate layers. The Sr2+ ion, the SiO4 tetrahedron and the bridging O atom of the disilicate unit are located on mirror planes whereas the TiO5 square-based pyramid is located on a fourfold rotation axis.

Related literature

For the crystal chemistry of fresnoites, see: Barbar & Roy (2012[Barbar, S. K. & Roy, M. (2012). J. Therm. Anal. Calorim. doi:10.1007/s10973-012-2336-0.]); Höche et al. (2002[Höche, T., Neumann, W., Esmaeilzadeh, S., Uecker, R., Lentzen, M. & Rüssel, C. (2002). J. Solid State Chem. 166, 15-23.]); ICDD (1989[ICDD (1989). PCPDFWIN. International Centre for Diffraction Data, Newtown Square, Pennsylvania, USA.]). For properties of Sr-fresnoites, see: Park & Navrotsky (2010[Park, T.-J. & Navrotsky, A. (2010). J. Am. Ceram. Soc. 93, 2055-2061.]). Atomic coordinates as starting parameters for the Rietveld refinement (Rietveld, 1969[Rietveld, H. M. (1969). J. Appl. Cryst. 2, 65-71.]) of the present phases were taken from Ochi (2006[Ochi, Y. (2006). Mater. Res. Bull., 41, 740-750.]); Goldschmidt & Thomassen (1923[Goldschmidt, V. M. & Thomassen, L. (1923). Skr. Nor. Vidensk. Akad. Oslo, 5, 1-48.]); Machida et al. (1982[Machida, K.-I., Adachi, G.-Y., Shiokawa, J., Shimada, M. & Koizumi, M. (1982). Acta Cryst. B38, 386-389.]); Mitchell et al. (2000[Mitchell, R. H., Chakhmouradian, A. R. & Woodward, P. M. (2000). Phys. Chem. Miner. 27, 583-589.]). For related strontium titanosilicates, see: Miyajima et al. (2002[Miyajima, H., Miyawaki, R. & Ito, K. (2002). Eur. J. Mineral. 14, 1119-1128.]). For synchrotron data analysis, see: Hammersley (1997[Hammersley, A. P. (1997). ESRF Internal Report No. ESRF97HA02T. ESRF, Grenoble, France.]); Hammersley et al. (1996[Hammersley, A. P., Svensson, S. O., Hanfland, M., Fitch, A. N. & Häusermann, D. (1996). High Pressure Res. 14, 235-248.]).

Experimental

Crystal data
  • Sr2TiSi2O8

  • Mr = 407.31

  • Tetragonal, P 4b m

  • a = 8.3200 (3) Å

  • c = 5.0239 (2) Å

  • V = 347.77 (2) Å3

  • Z = 2

  • Synchrotron radiation, [lambda] = 0.207549 Å

  • [mu] = 0.43 mm-1

  • T = 293 K

  • Cylinder, 20 × 0.7 mm

Data collection
  • In-house design diffractometer

  • Specimen mounting: capillary

  • Data collection mode: transmission

  • Scan method: continuous

  • 2[theta]min = 0.053°, 2[theta]max = 11.915°, 2[theta]step = 0.008°

Refinement
  • Rp = 0.052

  • Rwp = 0.073

  • Rexp = 0.031

  • RBragg = 0.093

  • [chi]2 = 31.068

  • 1476 data points

  • 71 parameters

  • 5 restraints

Data collection: local software; cell refinement: local software; data reduction: local software; program(s) used to solve structure: coordinates taken from a related compound; program(s) used to refine structure: FULLPROF (Rodriguez-Carvajal, 2001[Rodriguez-Carvajal, J. (2001). URL: http://www.ill.eu/sites/fullprof/]); molecular graphics: VESTA (Momma & Izumi, 2008[Momma, K. & Izumi, F. (2008). J. Appl. Cryst. 41, 653-658.]); software used to prepare material for publication: publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).


Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2699 ).


Acknowledgements

Thanks to Dr Hanns-Peter Liermann for help with data collection on P02.1.

References

Barbar, S. K. & Roy, M. (2012). J. Therm. Anal. Calorim. doi:10.1007/s10973-012-2336-0.
Goldschmidt, V. M. & Thomassen, L. (1923). Skr. Nor. Vidensk. Akad. Oslo, 5, 1-48.
Hammersley, A. P. (1997). ESRF Internal Report No. ESRF97HA02T. ESRF, Grenoble, France.
Hammersley, A. P., Svensson, S. O., Hanfland, M., Fitch, A. N. & Häusermann, D. (1996). High Pressure Res. 14, 235-248.  [CrossRef]
Höche, T., Neumann, W., Esmaeilzadeh, S., Uecker, R., Lentzen, M. & Rüssel, C. (2002). J. Solid State Chem. 166, 15-23.  [ISI] [CrossRef] [ChemPort]
ICDD (1989). PCPDFWIN. International Centre for Diffraction Data, Newtown Square, Pennsylvania, USA.
Machida, K.-I., Adachi, G.-Y., Shiokawa, J., Shimada, M. & Koizumi, M. (1982). Acta Cryst. B38, 386-389.  [CrossRef] [ISI] [details]
Mitchell, R. H., Chakhmouradian, A. R. & Woodward, P. M. (2000). Phys. Chem. Miner. 27, 583-589.  [ISI] [CrossRef] [ChemPort]
Miyajima, H., Miyawaki, R. & Ito, K. (2002). Eur. J. Mineral. 14, 1119-1128.  [ISI] [CrossRef] [ChemPort]
Momma, K. & Izumi, F. (2008). J. Appl. Cryst. 41, 653-658.  [ISI] [CrossRef] [ChemPort] [details]
Ochi, Y. (2006). Mater. Res. Bull., 41, 740-750.  [ISI] [CrossRef] [ChemPort]
Park, T.-J. & Navrotsky, A. (2010). J. Am. Ceram. Soc. 93, 2055-2061.  [ChemPort]
Rietveld, H. M. (1969). J. Appl. Cryst. 2, 65-71.  [CrossRef] [ChemPort] [details] [ISI]
Rodriguez-Carvajal, J. (2001). URL: http://www.ill.eu/sites/fullprof/
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.  [ISI] [CrossRef] [ChemPort] [details]


Acta Cryst (2013). E69, i1  [ doi:10.1107/S1600536812048921 ]

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