Reduced Cracking in Polycrystalline ZrO2-CeO2 Shape-Memory Ceramics by Meeting the Cofactor Conditions
32 Pages Posted: 9 May 2019 First Look: Under Review
Cracking is generally regarded as an unavoidable consequence of martensitic transformation in polycrystalline ZrO2-based ceramics. This shortcoming has limited ZrO2-based shape-memory ceramics (SMCs) to micron-sized single- or oligo-crystals to reduce bulk transformation stresses. In this paper we explore an alternate approach to reduce transformation-induced cracking by manipulating the crystallographic phase compatibility in polycrystalline ZrO2-CeO2 ceramics. For a range of compositions 12.5-15 mol% CeO2, we present lattice parameter measurements for the tetragonal and monoclinic phases from in situ X-ray diffraction, direct observation of lattice correspondences by electron backscatter diffraction, and calculations of interface and bulk compatibility. We identify ZrO2-13.5 mol% CeO2 as having preferred interface compatibility in that it closely meets the crystallographic cofactor conditions. This composition resists cracking through10 thermal cycles, whereas other compositions all crack. These results suggest that interface compatibility may contribute more strongly to transformation-induced cracking in ZrO2-based SMCs than previously believed and opens a strategy for designing crack-resistant polycrystalline SMCs.
Keywords: shape memory, ceramics, zirconia, cracking, compatibility
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