Thediffusion of oxygen in ultrafine grained, undoped monoclinic ZrO2 wasstudied using 18O as tracer and secondary ion mass spectroscopyprofiling. Samples with a relative mass density of 97%–99% andaverage crystallite sizes of 80 or 300 nm were preparedfrom Zr by sputtering, inert-gas-condensation, oxidation, in situ consolidation ofnanocrystalline (n-)ZrO2 powder and subsequent pressureless sintering at 950 or1050 °C in vacuum. Volume and interface diffusivities were directly determinedfrom the 18O diffusion profiles in n-ZrO2 in the typeB and type A regime of interface diffusion. The diffusionof 18O in interfaces in undoped n-ZrO2 is 103–104 timesfaster than in the bulk of the crystallites throughout thetemperature range of 450 to 950 °C studied. These diffusivities areindependent of the crystallite size in the range of 70–300nm. The activation energies QV = 2.29 eV and QB = 1.95 eV for the volume(QV) and interface diffusion (QB) are considerably higher than thediffusion activation energies found in the fast ion conductors Ca-or Y-stabilized ZrO2. Based on the present data on oxygendiffusion in ZrO2, the cation and anion diffusivities of otherbinary oxides are discussed.
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