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Observation of rare-earth segregation in silicon nitride ceramics at subnanometre dimensions


Silicon nitride (Si3N4) ceramics are used in numerous applications because of their superior mechanical properties1,2. Their intrinsically brittle nature is a critical issue, but can be overcome by introducing whisker-like microstructural features3,4. However, the formation of such anisotropic grains is very sensitive to the type of cations used as the sintering additives1,2,5. Understanding the origin of dopant effects, central to the design of high-performance Si3N4 ceramics, has been sought for many years. Here we show direct images of dopant atoms (La) within the nanometre-scale intergranular amorphous films typically found at grain boundaries, using aberration corrected Z-contrast scanning transmission electron microscopy. It is clearly shown that the La atoms preferentially segregate to the amorphous/crystal interfaces. First-principles calculations confirm the strong preference of La for the crystalline surfaces, which is essential for forming elongated grains and a toughened microstructure. Whereas principles of micrometre-scale structural design are currently used to improve the mechanical properties of ceramics, this work represents a step towards the atomic-level structural engineering required for the next generation of ceramics.

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Figure 1: Atomic-resolution scanning transmission electron microscope (STEM) images of an intergranular film (IGF) in La-doped β-Si3N4.
Figure 2: Magnified HAADF-STEM images of the interface between the IGF and the prismatic surface of an β-Si3N4 grain.


  1. Chen, I. W., Becher, P. F., Mitomo, M., Petzow, G. & Yen, T.-S. (eds) Silicon Nitride Ceramics—Scientific and Technological Advances (MRS Proceedings, Mater. Res. Soc. 287, Pittsburgh, Pennsylvania, 1993)

  2. Hoffmann, M. J. & Petzow, G. (eds) Tailoring of Mechanical Properties of Si3N4 Ceramics (NATO ASI Series E, Applied Sciences Vol. 276, Kluwer Academic, Dordrecht, 1994)

  3. Lange, F. F. Relation between strength, fracture energy, and microstructure of hot pressed Si3N4 . J. Am. Ceram. Soc. 56, 518–522 (1973)

    CAS  Article  Google Scholar 

  4. Tani, E., Umebayashi, K., Kishi, K. & Kobayashi, K. Gas-pressure sintering of Si3N4 with concurrent addition of Al2O3 and 5wt% rare earth oxide: High fracture toughness Si3N4 with fiber-like structure. Am. Ceram. Soc. Bull 65, 1311–1315 (1986)

    CAS  Google Scholar 

  5. Hoffmann, M. J., Gu, H. & Cannon, R. M. in Interfacial Engineering for Optimized Properties II (eds Carter, C. B., Hall, E. L., Briant, C. L. & Nutt, S.) 65–74 (MRS Proceedings 586, Mater. Res. Soc., Warrendale, Pennsylvania, 2000)

    Google Scholar 

  6. Becher, P. F. et al. Microstructural design of silicon nitride with improved fracture toughness: I, Effects of grain shape and size. J. Am. Ceram. Soc. 81, 2821–2830 (1998)

    CAS  Article  Google Scholar 

  7. Sun, E. Y. et al. Microstructural design of silicon nitride with improved fracture toughness: II, Effects of yttria and alumina additives. J. Am. Ceram. Soc. 81, 2831–2840 (1998)

    CAS  Article  Google Scholar 

  8. Sun, E. Y. et al. Debonding behavior between β-Si3N4 whiskers and oxynitride glasses with or without an epitaxial β-SiAlON interface layer. Acta Mater. 47, 2777–2785 (1999)

    CAS  Article  Google Scholar 

  9. Krämer, M., Hoffmann, M. J. & Petzow, G. Grain growth studies of silicon nitride dispersed in an oxynitride glass. J. Am. Ceram. Soc. 76, 2778–2784 (1993)

    Article  Google Scholar 

  10. Kleebe, H.-J. Structure and chemistry of interfaces in Si3N4 ceramics studied by transmission electron microscopy. J. Ceram. Soc. Jpn 105, 453–475 (1997)

    CAS  Article  Google Scholar 

  11. Gu, H., Pan, X., Cannon, R. M. & Rühle, M. Dopant distribution in grain-boundary films in calcia-doped silicon nitride ceramics. J. Am. Ceram. Soc. 81, 3125–3135 (1998)

    CAS  Article  Google Scholar 

  12. Ziegler, A., Kisielowski, C., Hoffmann, M. J. & Ritchie, R. O. Atomic resolution transmission electron microscopy of the intergranular structure of a Y2O3-containing silicon nitride ceramic. J. Am. Ceram. Soc. 86, 1777–1785 (2003)

    CAS  Article  Google Scholar 

  13. Batson, P. E., Dellby, N. & Krivanek, O. L. Sub-ångstrom resolution using aberration corrected electron optics. Nature 418, 617–620 (2002)

    ADS  CAS  Article  Google Scholar 

  14. Krivanek, O. L., Nellist, P. D., Dellby, N., Murfitt, M. F. & Szilagyi, Z. Towards sub-0.5 angstrom electron beams. Ultramicroscopy 96, 229–237 (2003)

    CAS  Article  Google Scholar 

  15. Pennycook, S. J. & Jesson, D. E. High-resolution Z-contrast imaging of crystals. Ultramicroscopy 37, 14–38 (1991)

    Article  Google Scholar 

  16. Pennycook, S. J. Structure determination through Z-contrast microscopy. Adv. Imag. Electron Phys. 123, 173–206 (2002)

    CAS  Article  Google Scholar 

  17. Averill, F. W. & Painter, G. S. Symmetrized partial-wave method for density functional cluster calculations. Phys. Rev. B 50, 7262–7267 (1994)

    ADS  CAS  Article  Google Scholar 

  18. Painter, G. S., Becher, P. F., Shelton, W. A., Satet, R. L. & Hoffmann, M. J. Differential binding energies: effects of rare-earth additions on grain growth of β-Si3N4 and ceramic microstructure. Phys. Rev. Lett. submitted

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We thank R. L. Satet and M. J. Hoffmann for supplying the silicon nitride ceramics used in this study. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under contract with UT-Battelle, LLC. N.S. is a fellow of the Japan Society for the Promotion of Science (JSPS).

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Correspondence to Naoya Shibata.

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T.R.G. is chief scientist in Pixon LLC. The remaining authors declare that they have no competing financial interests.

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Shibata, N., Pennycook, S., Gosnell, T. et al. Observation of rare-earth segregation in silicon nitride ceramics at subnanometre dimensions. Nature 428, 730–733 (2004).

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