RAMAN SPECTROMETRIC DETERMINATION OF THE OXYGEN SELF-DIFFUSION COEFFICIENTS IN OXIDES

New methods of determining the oxygen self-diffusion coefficients (D(o )) in oxides have been developed using Raman spectroscopy combined wi th the O-16-O-18 exchange technique. From the depth-profiles of the O- 18 concentration in the O-16-O-18 exchanged oxides, which was measured by Raman microscope with a spatial resolution of 5 mum, D(o) was det ermined for 2.8 mol% Y2O3-containing tetragonal zirconia polycrystals (the depth-profile method). Thus-obtained results are expressed as D(O ,D-P) = 1.82(-0.40)+0.41 x 10(-1).exp{-(139.3 +/- 0.2) [kJ/mol]/RT} [ cm2/s] in the temperature range of 700-950-degrees-C. We also determin ed D(o) for the same sample from the Raman spectrometric monitoring o f the ambient gas during the O-16-O-18 exchange reaction (the gas-moni toring method). Thus-obtained results are expressed as D(O,G-M) = 1.1 4(-0.04)+0.05 x 10(-2) exp{ - (117.5 +/- 0.4) [kJ/mol]/RT} [cm2/s] in the temperature range of 700-1165-degrees-C. The results obtained from the above two different methods virtually agree with each other, indi cating that reliable D(o) can be obtained by either of these two meth ods. We demonstrate that Raman spectroscopy is a useful tool for deter mining D(o) in oxides.