Optical properties of cubic hafnia stabilized with yttria.

The composition, transparency, refractive index, and infrared reflectance of yttria-stabilized cubic hafnia (c-HfO(2)) single crystals were measured. The material is transparent from the ultraviolet to the mid-infrared and for 9.6-mol % Y(2)O(3), the index is slightly smaller than for comparable cubic zirconia c-ZrO(2) or for diamond, but the dispersion (n(F) - n(c) = 0.02811) is larger than that of diamond. The index vs wavelength from 0.36 microm in the ultraviolet to 5.0 microm in the infrared is represented by a three-term Sellmeier formula to 1 x 10(-4). The temperature dependence of refractive index is similar to that of c-ZrO(2). The infrared reflectance spectrum is fitted in a classical dispersion analysis with seven oscillators derived from the transverse optical phonon as well as acoustic frequencies with splittings due to lowered symmetry derived from the randomly distributed stabilizer ions.