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

Abstract

β-Lu2Si2O7 is a promising candidate in the third generation of environmental barrier coating (EBC) materials for silicon-based ceramics due to its excellent high temperature environmental durability. However, the high temperature thermal and mechanical properties of β-Lu2Si2O7 are seldom reported, which hinders the design and evaluation of its EBC applications. In this paper, pure and dense β-Lu2Si2O7 sample was successfully fabricated and its mechanical properties, including Young's modulus, bulk modulus, shear modulus, Poisson's ratio, flexural strength, fracture toughness and hardness were investigated. The ball indentation test reveals that the main deformation mechanisms of β-Lu2Si2O7 at room temperature are deformation twinning and dislocation glide, which indicate that β-Lu2Si2O7 is a damage tolerant ceramic. In addition, the thermal expansion coefficient and thermal shock resistance were measured at high temperatures. β-Lu2Si2O7 possesses excellent high temperature elastic stiffness up to 1470°C, and the critical temperature difference for thermal shock resistance is 270K.