Size-induced room temperature softening of nanocrystalline yttria stabilized zirconia

Lin Feng, Arseniy Bokov, Shen J. Dillon, Ricardo H.R. Castro

Research output: Contribution to journalArticlepeer-review


Nanocrystalline oxides exhibit exceptional resistance to plastic deformation, manifesting increased strength and hardness with reduced grain size that qualitatively follows the so-called Hall-Petch relationships. However, below a critical grain size, softening has been observed to occur, in the so-called inverse Hall-Petch regime. The mechanisms underlying these phenomena are still not well understood in oxides. Here we observe, using nanopillar compression, that the yield strength initially increases with decreasing grain size for yttria-stabilized zirconia ceramics produced by high-pressure spark plasma sintering. A hardening-to-softening transition occurs at grain sizes below ≈21 nm. The experiments indicate that this transition depends on strain rate, and the onset of the decrease in yield strength occurs before any shear fracture begins. Nanopillar compression combined with in situ electron diffraction demonstrates the onset of softening coincides with an increase in the amount of crystallographic rotation per unit strain, suggesting a change in deformation mechanism.

Original languageEnglish (US)
Pages (from-to)2050-2055
Number of pages6
JournalJournal of the European Ceramic Society
Issue number5
StatePublished - May 2020


  • Ceramics
  • Grain rotation
  • Hardness
  • Nanocrystalline
  • TEM

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry


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