First‐principles study of thermophysical properties of polymorphous YTaO₄ ceramics

Abstract

Yttrium tantalate ceramics with ferroelasticity are potential candidates for thermal barrier coating (TBC) ceramics. During the phase transition process, there are three main phases with monoclinic (I2/a), monoclinic-prime (P2/a), and tetragonal structures (I 41 /a), and a comprehensive understanding of their thermophysical properties is required. In this study, the thermal and mechanical properties of polymorphous yttrium tantalate (YTaO 4 ) ceramics are systematically investigated under finite temperature by performing first-principles calculations combined with quasi-harmonic approximation. The first-principle study results show that the volume change from M' to T phase is 12.85 Å 3 to 12.95 Å 3 per atom, whereas the T to M is 12.95 Å 3 to 12.84 Å 3 per atom, and the change is less than 1%, showing that this process produces almost no volume change.However, the thermal expansion coefficients (TECs) and Young's modulus vary greatly, the TECs value of M YTaO 4 is about 11.13 × 10 −6 K −1 , which is smaller than T YTaO 4 as the value 12.01 × 10 −6 K −1 , and the Young's modulus values of M, M', and T phases are 140. 34, 156.68, and 123.29 GPa, respectively. Lastly, the calculated O-Ta bond is stronger than the O-O and O-Y bonds according to the mean bond population and average bond length, resulting in a higher modulus. This work will not only expand the internal mechanism of the thermophysical properties of YTaO 4 , but also provides support for the design and application of TBC systems.

Mechanical Properties and Toughening Mechanisms of a Promising Zr-Y-Ta-O Composite Ceramics

“…Table 3 lists the values of these parameters for calculating residual stress. The TEC of fluorite phase is (9.6×10 −6 K −1 ), lower than that of M-YTaO4 phase (10.7×10 −6 K −1 ) [26] . The Young's modulus and Poisson's ratio of M-YTaO4 phase is (177 GPa and 0.35), that of fluorite phase were (210GPa and 0.3) [27] .…”

“…The T→M phase transition of YTaO4 being ferroelastic is of a continuous second order nature. Previous research states that the volume variation in YTaO4 T→M phase transition is so tiny that it can be omitted [33] . Ferroelastic domain exists of parallel striped structured in pure YTaO4 ceramic(samples YT5) and the SEM results are shown in Fig.…”

Capturing and visualizing the phase transition mediated thermal stress of thermal barrier coating materials via a cross-scale integrated computational approach

“…The calculated equilibrium lattice parameters (a, b, c), lattice dihedral angle (β), and equilibrium volume (V) summarized in Table 1 indicate that the calculated lattice parameters are slightly larger than the experimental values [33,38], which may be due to the overestimation of lattice parameters by the GGA exchangecorrelation functional [69]. The results indicate that the lattice Capturing and visualizing the phase transition mediated thermal stress of thermal barrier coating materials via a cross-scale integrated ... constant gradually decreases as the ionic radius of RE 3+ decreases.…”

“…For m-GdTaO 4 and m'-GdTaO 4 , there are no imaginary frequencies observed along the high symmetry path in the phonon dispersion, signifying their inherent stability at 0 K [73,74]. Conversely, the phonon dispersion of t-GdTaO 4 shows the presence of an Table 1 Calculated lattice parameters (a, b, c, lattice dihedral angle (β), and volume (V)) of m-RETaO 4 , m'-RETaO 4 , and t-RETaO 4 (RE = Nd, Sm, Gd, Dy, Ho, Er) in comparison with experimental data [33,38] and calculation data [70] Compound Combined with our previous work [35,36], the t phase is considered to be thermodynamically stable at high temperatures. It is demonstrated that the RETaO 4 ceramics undergo the phase transformation during the heating and cooling process.…”

Insights on Elastic Anisotropy and Thermal Properties of Mg–Ti–O Compounds from First‐Principles Calculations

“…[ 16 ] Using first principles combined with the quasiharmonic approximation, Zhou et al studied the structural, thermodynamic, thermal, and mechanical properties of polymorphous YTaO 4 at finite temperatures. [ 17 ] In this article, the first‐principles calculation methods were performed to investigate the elastic anisotropy and thermal properties of the Mg–Ti–O compounds. The physics parameters, such as elastic compliance/stiffness constants, bulk/shear/Young's modulus and their anisotropies, Poisson's ratio, Debye temperature, sound velocities, and thermal conductivity were obtained theoretically.…”