Mechanical properties of zirconia, doped and undoped yttria-stabilized cubic zirconia from first-principles

Abstract Density functional theory calculations investigate the mechanical properties of: cubic ( c ), tetragonal ( t ) and monoclinic ( m ) zirconia (ZrO 2 ); cubic yttria-stabilized zirconia ( c -YSZ); c -YSZ doped with TiO 2 , MnO 2 , CaO and NiO. These find the elastic constants, elastic compliances, bulk, shear and Young's modulus for the three phases of zirconia together with the ideal strength of c -ZrO 2 . The ideal strength of c -ZrO 2 for strain in the [ 100 ] direction (84.3 GPa) being significantly higher than in the [ 110 ] (30.5 GPa) and [ 111 ] directions (9.87 GPa) is attributed to change in the bond angle reducing the internal strain on the bonds. Adding Y 2 O 3 to c -ZrO 2 decreases the ideal strength, particularly in the [100] direction, namely to respectively 11.1 and 28.8 GPa for 6.67 and 14.29 mol % Y 2 O 3 . Doping c -YSZ with TiO 2 , MnO 2 , CaO and NiO further reduces the ideal strength, with the lowest values for TiO 2 (7.16–7.88 GPa). The significant decrease in the ideal strength of c -YSZ and doped c -YSZ compared to c -ZrO 2 in the [100] direction is attributed to the weakening of the ZrO 2 framework by the oxygen vacancies.