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

The thermal and mechanical properties of -Yb2Si2O7 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 -Yb2Si2O7 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)=(3.57 +/- 0.18)x10(-6)K(-1), (b)=(2.49 +/- 0.14)x10(6)K(-1), and (c)=(1.48 +/- 0.22)x10(-6)K(-1) (673-1273K). A low thermal conductivity of similar to 2.1W (mK)(-1) at 1273K has been confirmed. The unique combination of these properties endow it a potential candidate for thermal barrier coating (TBC)/environmental barrier coating of silicon-based ceramics.