Abstract
The mechanical and thermal properties of Y4Al2O9 were predicted using a combination of first-principles and chemical bond theory (CBT) calculations. Density functional theory (DFT) computations were performed for the structural, mechanical, and thermal properties, and the results were confirmed by chemical bond theory. Based on the calculated equilibrium crystal structure, heterogeneous bonding nature has been revealed, i.e., Al-O bonds are stronger than Y-O bonds. Low second-order elastic constants c44, c55, and c66 demonstrate the low shear deformation resistance. Low G/B ratio suggests that Y4Al2O9 is a damage tolerant ceramic. Y4Al2O9 shows anisotropy in elastic behavior based on the discussion of direction dependence of Young's modulus. The hardness is predicted to be 10.2 GPa from calculated elastic moduli. The thermal expansion coefficient (TEC) calculated by chemical bond theory is 7.51×10 6 K 1 . In addition, the minimum thermal conductivity of Y4Al2O9 is estimated to be 1.13 W·m 1 ·K 1 , and the thermal conductivity decreases with
Highlights
Yttria-stabilized zirconia (YSZ) is a widely used thermal barrier coating on turbine blades in gas-turbine engines to increase the operating temperature and the efficiency and power of the engines [1]
The chemical bonding characteristics, elastic stiffness, thermal expansion coefficient, and thermal conductivity of Y4Al2O9 were investigated by first-principles calculations and chemical bond theory
The theoretical results reveal the heterogeneous bonding nature of Y4Al2O9, i.e., Al–O bonds are stronger than Y–O bonds
Summary
Yttria-stabilized zirconia (YSZ) is a widely used thermal barrier coating on turbine blades in gas-turbine engines to increase the operating temperature and the efficiency and power of the engines [1]. The instability of metastable tetragonal-prime structure due to the decomposition into a mixture of tetragonal and cubic zirconia limits the application of YSZ at higher operating temperatures [2]. Searching for new thermal barrier coating (TBC) materials with low Recent works have demonstrated that yttrium aluminates are promising candidates for TBCs due to their superior high temperature stability, and mechanical and thermal properties [5,6]. Yttrium aluminum garnet (i.e., Y3Al5O12, YAG) is stable with Al2O3 [5], which is the thermally grown oxide formed on Ni-based superalloys. Besides YAG, Y4Al2O9 (YAM) is a stable compound in the Y–Al–O www.springer.com/journal/40145
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
