High temperature microhardness of single crystal mullite

Waltraud M. Kriven, Lay Foong Siah, Martin Schmücker, Hartmut Schneider

Research output: Contribution to journalArticlepeer-review


The microhardness (H) of single crystal, orthorhombic mullite was measured on (010) and (001) faces from room temperature up to 1400°C. The microhardness versus temperature curves display sigmoidal shapes. The mean microhardness at room temperature is ∼16 Gpa and it decreases with temperature to H is ∼13 GPa at 300°C. At >300°C, the microhardness is only slightly reduced with temperature to H is ∼10 GPa at 1000°C. Above this temperature limit, it markedly decreases again, to a mean value of ≈6 GPa at 1400°C. Up to ∼1000°C the (010) and (001) microhardnesses are very similar. Above ∼1000°C, however, the hardness gradually becomes anisotropic, with H(010) being twice as high as H(010) at 1400°C (H(010) ∼ 8 GPa, H(010) ∼ 4 GPa).

Original languageEnglish (US)
Pages (from-to)970-972
Number of pages3
JournalJournal of the American Ceramic Society
Issue number5
StatePublished - May 2004

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry


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