Raman scattering study of thermally reduced stabilized cubic zirconia

We investigated the Raman spectra of thermally reduced and untreated Y- and Ca-stabilized cubic zirconia. A substantial decrease in Raman activity was observed in the acoustic mode region upon reduction. Analyses of these spectra as a phonon density of states and of the observed spectral changes indicate that the reduced states are more ordered than the untreated one. This is consistent with a nonrandom arrangement of vacancies, which produces the superposition of periodic sequences of vacancies within domains. This, in turn, causes the increment in coherence length of phonons that is manifested as a decrease in acoustic mode activity.