Abstract
In an effort to transformation toughen alumina surfaces, Y+ was implanted in sapphire previously implanted with Zr+ at a dose of 1.25 x 1017 ions/cm2. The Y+ implant doses ranged from 1 to 10 x 1015 ions/cm2 and the double implants were labelled Y+/Zr+/A12O3. Annealing in the air at 1400‡ C produced a uniform surface film of polycrystalline ZrO2 doped with Y2O3 which had a grain size of 0.1 to 1.0 Μm. From x-ray diffraction (XRD), the ZrO2 phases transitioned from monoclinic to tetragonal to cubic as the Y2O3 content increased from 0 to 4 m/o based on zirconia content. Obtaining only cubic zirconia was surprising, because pure cubic ZrO2 should result only above 9.2 m/o Y2O3. The ratios of Y to Zr measured by electron spectroscopy for chemical analysis (ESCA) depth profiling for the high dose Y+ implant was equivalent to 10 m/o Y2O3 in ZrO2 rather than the implanted ratio of 4 m/o. The higher than expected Y concentrations agreed with the XRD results and were probably produced by Zr removal by ion milling during the high Zr+ dose implant. Surface fracture toughness, as measured by indentation, decreased as yttria content increased because elimination of monoclinic ZrO2 from the precipitate phases prevented a surface compression layer created by the tetragonal to monoclinic ZrO2 transition on cooling from annealing temperatures.
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Cochran, J.K., Pope, S.G., Legg, K.O. et al. Control of zirconia surface phases in annealed alumina with Y+/Zr+ implantation ratios. J. Materials Engineering 11, 141–147 (1989). https://doi.org/10.1007/BF02834462
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DOI: https://doi.org/10.1007/BF02834462