Large mechanical properties enhancement in ceramics through vacancy-mediated unit cell disturbance
Zhuo Chen, Yong Huang, Nikola Koutná, Zecui Gao, Davide G. Sangiovanni, Simon Fellner, Georg Haberfehlner, Shengli Jin, P.H. Mayrhofer, Gerald Kothleitner, Zaoli Zhang
Abstract
Tailoring vacancies is a feasible way to improve the mechanical properties of ceramics. However, high concentrations of vacancies usually compromise the strength (or hardness). We show that a high elasticity and flexural strength could be achieved simultaneously using a nitride superlattice architecture with disordered anion vacancies up to 50%. Enhanced mechanical properties primarily result from a distinctive deformation mechanism in superlattice ceramics, i.e., unit-cell disturbances. Such a disturbance substantially relieves local high-stress concentration, thus enhancing deformability. No dislocation activity involved also rationalizes its high strength. The work renders a unique understanding of the deformation and strengthening/toughening mechanism in nitride ceramics.