Surface deformation of sapphire crystal

R. Nowak, T. Sekino, K. Niihara

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)


The anisotropic surface deformation of sapphire has been studied by means of depth-sensing indentation experiments with a small-radius spherical indenter loaded onto the basal (0001) and the prismatic (1010) planes of the crystal. The results of the low-speed high-accuracy continuous-indentation test have revealed significant differences in the mechanical behaviour of alumina crystals when indented on different crystallographic planes. A special effort has been made to clarify the origin of the characteristic discontinuities appearing in the loading part of the indentation hysteresis loops observed for fire experiments performed on the (0001) as well as (10T0) planes of sapphire. It was concluded that the large ‘step-in’ reflects the formation of a twin in α-alumina crystals deformed with a blunt indenter. A new resolved shear stress model has been proposed in order to meet the requirements of spherical indentation. The results of numerical calculations predicted the deformation systems activated in the vicinity of spherical indentation. The prediction correlated with the observations of residual impressions.

Original languageEnglish
Pages (from-to)171-194
Number of pages24
JournalPhilosophical Magazine A: Physics of Condensed Matter, Structure, Defects and Mechanical Properties
Issue number1
Publication statusPublished - 1996 Jul

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Materials Science(all)
  • Condensed Matter Physics
  • Physics and Astronomy (miscellaneous)
  • Metals and Alloys


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