Characterization of a new Nb–silicide (δ-Nb₁₁Si₄) in Nb–Si binary systems

Abstract

A new Nb–silicide, δ-Nb₁₁Si₄, identified as a second phase precipitated from a Nb–Si solid solution, was characterized by combining crystallographic analysis with first-principles calculations. The crystal structure was determined as a body-centered orthorhombic system with space group Immm using transmission electron microscope (TEM). Based on the crystallographic relationship between the δ and Nb phases, // {200}_Nb and // ⟨001⟩_Nb, eight possible unit cells were proposed, which were optimized by first-principles calculations. By analyzing the experimental and calculated data, we obtained the final unit cell of the δ phase, which was confirmed by high-resolution TEM images. In addition, density of states and electron density difference of δ-Nb₁₁Si₄ revealed that the δ structure was in a metastable state at low temperature because not all the bonding states were filled.

Keywords:

• microstructure
• precipitation
• niobium–silicide
• orientation relationship
• transmission electron microscopy

Acknowledgements

This work was supported by the National Natural Science Foundation of China and Special Funds for the Major State Basic Research Projects of China Grant No. 2006CB600905.

Notes

Note

1. See details in supplementary document.