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Identification and lattice location of oxygen impurities in α-Si3N4

J. C. Idrobo,1,2,3, M. P. Oxley,1,2 W. Walkosz,3 R. F. Klie,3 S. Ög?üt,3 B. Mikijelj,4 S. J. Pennycook,1,2 and S. T. Pantelides1,2

Appl. Phys. Lett. 95, 164101 (2009)

For over 40 years impuriies have been believed to stabilize the ceramic α-Si3N4 but there is no direct evidence for their identity or lattice location. In bulk materials electron microscopy can generally image heavy impurities. Here we report direct imaging of N columns in α-Si3N4 that suggests the presence of excess light elements in specific N columns. First-principles calculations rule out Si or N interstitials and suggest O impurities, which are then confirmed by atomically resolved electron-energy-loss spectroscopy. The result provides a possible explanation for the stability of α-Si3N4 with implications for the design of next-generation structural ceramics.


(a) Z-contrast image of α-Si3N4 with line trace across the arrowed position showing unexpectedly strong intensity from particular N columns. (b) EELS from these columns reveals the presence of O (red trace). The black trace is the spectrum obtained from scanning a larger region, when no O is detectable.
   
 

1Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA
2Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
3Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, USA
4Ceradyne Inc. Costa Mesa, California 92626, USA

   
 

 Oak Ridge National Laboratory