Theoretical Prediction and Experimental Investigation on the Thermal and Mechanical Properties of Bulk β‐Yb₂Si₂O₇

Abstract

The thermal and mechanical properties of b-Yb 2 Si 2 O 7 were investigated using a combination of first-principles calculations and experimental investigations. Theoretically, anisotropic chemical bonding and elastic properties, weak interatomic (010) and (001) planes in the crystal structure, damage tolerance, and low thermal conductivity are predicted. Experimentally, preferred orientation, superior mechanical properties, and damage tolerant behavior for hot-pressed bulk b-Yb 2 Si 2 O 7 are approved. Slipping along the weakly bonded {010}, {001}, or {100} planes, grain delamination, buckling, and kinking of nanolaminated grains are identified as main mechanisms for damage tolerance. The anisotropic linear thermal expansion coefficients (CTEs) are: a a = (3.57 AE 0.18) 3 10 À6 K À1

Preparation, mechanical, and thermal properties of a promising thermal barrier material: Y4Al2O9

“…(5), the damage tolerance of YAM is determined 0.25. This value is slightly lower than those of -Yb 2 Si 2 O 7 (0.39) [14] and -Y 2 Si 2 O 7 (0.37) [15], but still warants the damage tolerance of YAM.…”

Synthesis, mechanical and thermal properties of a damage tolerant ceramic: β-Lu2Si2O7

“…Therefore, H v /E, G/B and K IC /σ can be taken as useful indicators of the damage tolerance of materials. The values of H v /E, G/B, and K IC /σ of ␤-Lu 2 Si 2 O 7 and some damage tolerant ceramics are shown in Table 4 [20,23]. The H v /E value for ␤-Lu 2 Si 2 O 7 is lower than those of ␥-Y 2 Si 2 O 7 and ␤-Yb 2 Si 2 O 7 , and is close to that of the machinable ceramic LaPO 4 .…”

“…The Y O bond is weaker and readily stretches and shrinks; and Si O bond is stronger and more rigid. The relatively softer YO 6 It is well established that anisotropic chemical bonding is reflected by the anisotropy of Young's modulus [20]. To reveal the anisotropy of chemical bonding and the resulting anisotropic elastic stiffness, elastic constants are listed in Table 2 modulus was calculated and the results are presented in Fig.…”

“…2(b) shows, the Young's modulus on the (1 0 0) atomic plane shows weaker anisotropy than those on other planes. The anisotropic elastic stiffness of ␤-Lu 2 Si 2 O 7 is mainly attributed to the heterogeneity of chemical bonds [20].…”

“…Hampshire proposed that the CFS can be calculated by: CFS = Z c /r c 2 , where Z c is ionic charge of the cation and r c is ionic radius of cation [24,25]. The ionic radius of the lanthanides decreases with increasing atomic number [19,20]. Actually, both ␥ and ␤ phases consist of corner sharing Si 2 O 7 double tetrahedra and RE atoms, and one can transform to the other by shuffling of the RE atoms and movement or rotation of the double tetrahedral [26].…”