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. Zr₂(Al(Si))₄C₅ and Zr₃(Al(Si))₄C₆ 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 Zr₂(Al(Si))₄C₅ 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, Zr₂(Al(Si))₄C₅ retained a high Young’s modulus up to about 1580 °C, which can be attributed to its comparable activation energy of lattice drag process to that of ZrC.