PRESSURE-DEPENDENCE OF THE REFRACTIVE-INDEX OF MONOCLINIC AND YTTRIA-STABILIZED CUBIC ZIRCONIA

The pressure dependence of the refractive index of monoclinic and yttr ia-stabilized cubic zirconia was measured up to 3 and 8 GPa, respectiv ely, using an interferometric method with the diamond-anvil cell. The experimental results show a practically linear behavior for both cryst alline structures. For cubic zirconia, the refractive index remains pr actically constant under pressure, while for the biaxial monoclinic ph ase, one component of the refractive index decreases and the other com ponent increases with pressure, despite the rather isotropic lattice c ompression in the corresponding crystalline directions. The behavior o f the electronic polarizability of the oxygen ion was investigated thr ough the Lorentz-Lorenz relation, yielding the following Mueller param eters: for the cubic phase Lambda(0) = 1.02, and for the monoclinic ph ase Lambda(0) = 1.05 for the component nearly parallel to the b direct ion, and Lambda(0) = 0.85 for the component in the direction of the pr ojection of the ''a'' axis on the sample plane. In the case of monocli nic zirconia, the behavior of the polarizability under pressure is abo ut 20% more anisotropic than the compression of the respective lattice parameters, indicating a distinct effect of the interatomic interacti ons over the oxygen ions for the two directions under consideration.