Effect of Ta 2 O 5 , Nb 2 O 5 , and HfO 2 Alloying on the Transformability of Y 2 O 3 ‐Stabilized Tetragonal ZrO 2

The addition of Ta 2 O 5 , Nb 2 O 5 , and HfO 2 enhanced the transformability of Y 2 O 3 ‐stabilized tetragonal ZrO 2 polycrystal (Y‐TZP), which was indicated by an increase in phase transformation temperatures and fracture toughness of Y‐TZP. Comparison of the alloying effects of these oxides on the transformability and crystal structure of Y‐TZP suggested that an alloying oxide which increases the c/a axial ratio (tetragonality) of TZP also increases the transformability. Empirical equations to predict the tetragonality are proposed. Calculated tetragonalities showed good agreement with measured values in the systems ZrO 2 ‐Y 2 O 3 ‐Ta 2 O 5 , ‐Nb 2 O 5 , and ‐HfO 2 .