Structure of yttria stabilized zirconia beads produced by gel supported precipitation
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Yttria stabilized zirconia (YSZ) is one of the inert matrix candidates selected for investigation as host matrix for minor actinide (MA) transmutation. The structural properties of (Zr0.84, Y0.16)O1.92 beads prepared by a sol–gel method for MA infiltration, are characterized as calcined (850 °C) and sintered (1,600 °C) beads. The calcined YSZ beads are fine-grained and homogenous over the entire sphere and are surrounded by a uniform outer layer of approximately 30 μm thickness. After sintering at 1,600 °C, the beads are compacted to 51% of their initial volume and exhibit a granular structure. The thermal expansion is nearly linear for the calcined material, but shows a parabolic behavior for the sintered (1,400 °C) beads. In addition, the thermal expansion of calcined material is 20–25% less than after sintering. During heating up to 1,400 °C, two processes can be distinguished. The first occurs between 900 and 1,000 °C and is related to an increase in unit cell order. The second process involves grain-growth of the less crystalline calcined material between 1,100 and 1,300 °C. These results have implications for preparation of YSZ and its use as an inert MA transmutation matix.
KeywordsYttria Stabilize Zirconia Minor Actinide Inert Matrix Fuel Sintered Bead Uniform Outer Layer
We would like to acknowledge the assistance of Y. Martin Alvarez and H. Hein in the preparation of samples, J. Rothe and K. Dardenne for assistance using the INE-beamline, and thank the ANKA Angstroemquelle Karlsruhe for providing beamtime for the EXAFS measurements. X-ray tomography at ORNL was sponsored by the Office of Nuclear Energy, Science and Technology and Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract No. DE-ACO5-00OR22725.
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