High temperature optical spectroscopy of cubic holmium doped zirconia, Zr(0.78)Y(0.21)Ho(0.01)O(1.90).

The electronic absorption spectra of a Zr(0.78)Y(0.21)Ho(0.01)O(1.90) single crystal have been measured in in situ conditions between room temperature and 1289 K. The evolution of the spectra with rising temperatures is characterised by an overall increase in intensity. Notably the intensities of the (5)I(8) --> (5)F(2), (5)I(8) --> (5)S(2) and (5)I(8) --> (5)G(6) transitions increase by factors of two to three. The evaluation of the spectral parameters favours the conclusion that the intensity increases are due to vibronic coupling associated with effective frequencies ranging between 1 x 10(13) and 5 x 10(13) s(-1) (330 cm(-1) and 1670 cm(-1)). The changes in the optical spectra are reversible and are not connected with structural changes in the material.