Phase Stability and Physical Properties of Cubic and Tetragonal ZrO2 in the System ZrO2-Y2O3-Ta2O5

Abstract

The cubic (c­ZrO2) and tetragonal zirconia (t­ZrO2) phase stability regions in the system ZrO2？Y2O3？Ta2O5 were delineated. The c­ZrO2 solid solutions are formed with the fluorite structure. The t­ZrO2 solid solutions having a c/a axial ratio (tetragonality) smaller than 1.0203 display high fracture toughness (5 to 14 MPa · m1/2), and their instability/transformability to monoclinic zirconia (m­ZrO2) increases with increasing tetragonality. On the other hand, the t­ZrO2 solid solutions stabilized at room temperature with tetragonality greater than 1.0203 have low toughness values (2 to 5 MPa · m1/2), and their transformability is not related to the tetragonality. Copyright ？ 1991, Wiley Blackwell. All rights reserved