Stability of nanovoids in amorphous Si₃B₃N₇

Abstract

The amorphous ceramic material a-Si₃B₃N₇ possesses a rather low density (≈1.9 g/cm³) compared with, for example, the weighted average of the crystalline binary compounds Si₃N₄ and BN (≈2.8 g/cm³). Our simulations show that nanosize cavities, which are created during synthesis via the sol–gel route, can survive for a very long time even at elevated temperatures (up to 1500 K), and are thus the most likely explanation for the low density of a-Si₃B₃N₇. Furthermore, we find that, at low temperatures, the application of very high pressures exceeding 10 GPa should lead to a considerable irreversible densification of the material up to ≈2.8 g/cm³.

Acknowledgements

We would like to thank T. Jäschke and P. Balog for interesting discussions. Funding was kindly provided by the DFG via SFB408.