High temperature optical spectroscopy investigations on Zr0.78Y0.18Sm0.04O1.89 and Zr0.78Y0.018Ho0.04O1.89 single crystals.

Results are reported from a temperature dependent optical study of the title compounds performed at temperatures up to 1323 K. Absorption maxima and integrated absorption of rare earth f-f transitions exhibit a considerable temperature dependence, which is quantitatively described in the framework of the optical high temperature spectroscopy of d-ions. A strong, reversible band gap shift of doped and pure YSZ is observed and evaluated according to the Tauc equation. Single crystals of the title compounds were prepared by the skull melting method. Their linear expansion coefficients were determined by high-temperature X-ray diffraction.