Examining crystallographic orientation dependence of hardness of silica stishovite

Sheng-Nian Luo, J.G. Swadener, Chi Ma, Oliver Tschauner

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We conducted nanoindentation to explore the hardness and elastic properties of silica stishovite, synthesized at high pressure and quenched to ambient conditions. A total of 10 crystallographic orientations were examined on selected grains with a maximum load of 4 or 20 mN. We observed discontinuity in the load-displacement curve (pop-in) for the [2 5 over(1, -)] and [6 2 over(1, -)] grains subjected to a maximum load of 20 mN. The single-crystal hardness at high plastic deformation is quasi-isotropic with an average of 32 ± 1 GPa, similar to the polycrystalline hardness reported earlier; the theoretical hardness determined from the experiments is about 54 ± 3 GPa. These two hardnesses suggest that stishovite is one of the hardest oxides. The measured indentation moduli are close to the predictions at low load (minor plasticity) but are considerably lower at high load (high plasticity). Both indentation hardness and modulus decrease with increasing plasticity. Our results underscore the necessity of considering the degree of plastic deformation when interpreting hardness and elastic moduli from indentation experiments.
Original languageEnglish
Pages (from-to)138-142
Number of pages5
JournalPhysica B: Condensed Matter
Issue number2
Early online date17 Jun 2007
Publication statusPublished - 1 Nov 2007


  • silica stishovite
  • nanoindentation
  • hardness
  • elastic modulus


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