Chapter 84. Temperature Dependent Brittle Fracture of Undoped and Impurity Doped Sapphire Fibers

  1. John B. Wachtman Jr.
  1. Haluk Sayir,
  2. Ah Sayir and
  3. K. Peter D. Lagerlöf

Published Online: 28 MAR 2008

DOI: 10.1002/9780470314180.ch84

Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8

Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8

How to Cite

Sayir, H., Sayir, A. and Lagerlöf, K. P. D. (1993) Temperature Dependent Brittle Fracture of Undoped and Impurity Doped Sapphire Fibers, in Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314180.ch84

Author Information

  1. Dept. of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106

Publication History

  1. Published Online: 28 MAR 2008
  2. Published Print: 1 JAN 1993

ISBN Information

Print ISBN: 9780470375266

Online ISBN: 9780470314180

SEARCH

Keywords:

  • crystal;
  • degradation;
  • nucleation;
  • crystallography;
  • stress intensity

Summary

The fracture strength as a function of temperature of single crystal alumina fibers oriented along the c-axis have been measured in air using three-point bending. The strength degradation observed in undoped sapphire at intermediate temperatures was removed by impurity doping with MgO, TiO2, and MgO+TiO2 co-doping. Since the impurities are segregated to the surface of the fibers, which in turn gives rise to surface residual compressive stresses, stress corrosion effects could be the reason for the fracture strength degradation at intermediate temperatures of undoped fibers. The fracture behavior have been evaluated in terms of models based on slow crack-growth of existing surface flaws and the nucleation and growth of twins as the strength limiting flaws.