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 ac tivity was observed in the acoustic mode region upon reduction. Analys es of these spectra as a phonon density of states and of the observed spectral changes indicate that the reduced states are more ordered tha n the untreated one. This is consistent with a nonrandom arrangement o f vacancies, which produces the superposition of periodic sequences of vacancies within domains. This, in turn, causes the increment in cohe rence length of phonons that is manifested as a decrease in acoustic m ode activity. (C) 1997 American Institute of Physics.