Georgia Institute of Technology Atlanta United States
Green processing, sintering and post-HIPing methodologies were developed for producing Lu2O3 ceramics of good transparency, up to 8 mol Yb2O3, using commercial powders not exposed to further chemical processing. Restricting the extent of sintering to relative densities at the threshold of closed porosity facilitated the highest relative density, highest transparency, post-HIPed specimens. Use of other lot numbers of lutetia, as well as less expensive sources, required a deeper understanding of processing to produce ceramics of equal transparency. Ball milling with stabilized zirconia media yielded nano-scale powder with no measurable impurity aquisition. Spray-drying acetone-based slurries of these powders with soluble organic binderplasticizer facilitated sintering to a closed porosity state at lower temperatures. Black spots dispersed in otherwise transparent samples required adjustment of O2 thermolysis temperatures to eliminate what was interpreted as carbon char left behind from pyrolysis of processing organic liquids. Suggested follow on work is to change the organic additives and suspending fluid to eliminate these spots, and alteration of pressing conditions, or changing to slip casting, to eliminate large-scale porosity from remnants of spray dried granules.