ELASTIC CONSTANTS AND INTERATOMIC BINDING IN YTTRIA-STABILISED ZIRCONIA

Zirconia (ZrO2) can be forced into a cubic fluorite structure by the addition of more than 7 mol % yttria (Y2O3). The elastic stiffness constants of cubic zirconia single crystals containing 8 and 12 mol % yttria have been determined between 77 and 300° K by an ultrasonic pulse echo technique. Elastic constants are almost temperature-independent and at 77° K are for the 8 and 12 mol % respectively: C11=2.04, C12=0.87, C44=1.58; C11=2.23, C12=0.973, C44=1.54 (units: 1012 dynes cm-2). Compressibilities and elastic compliances are also presented. The data provide a basis for discussion of crystalline stability and the nature of the interatomic forces. The decreasing cubic lattice stability as the yttria content is reduced is demonstrated quantitatively. An ionic model closely characterises the binding forces. The repulsive energy is about 12% of the Madelung attractive energy. Debye temperatures calculated from the elastic constant data extrapolated to 0° K are 595 and 604° K for the 8 and 12 mol % respectively. © 1969 Chapman and Hall Ltd.