Atomic-scale microstructure and elastic properties of quaternary Zr–Al–Si–C ceramics

Transmission electron microscopy characterizations and elastic properties of two quaternary carbides, i.e. Zr(2()Al(Si))(4) C(5) and Zr(3)(Al(Si))(4)C(6) are reported. The space group and atomic-scale microstructures of both compounds were determined using a combination of selected area electron diffraction, convergent beam electron diffraction, high-resolution transmission electron microscopy and Z-contrast scanning transmission electron microscopy. In addition, the combined experimental and theoretical studies on elastic properties for Zr(2)(Al(Si))(4)C(5) are presented. A full set of second-order elastic constants, bulk modulus, shear modulus, and Young's modulus were calculated using first-principles calculations. Both experimental and theoretical works demonstrated that quaternary Zr-Al-Si-C ceramics possess close elastic properties to ZrC. Furthermore, Zr(2)(Al(Si))(4)C(5) retained a high Young's modulus up to about 1580 degrees C, which can be attributed to its comparable activation energy of lattice drag process to that of ZrC. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.