On the Effect of Local Grain-Boundary Chemistry on the Macroscopic Mechanical Properties of a High Purity Y2O3-Al2O3-Containing Silicon Nitride Ceramic: Role of Oxygen
The effects of grain-boundary chemistry on the mechanical properties were investigated on high-purity silicon nitride ceramics, specifically involving the role of oxygen. Varying the grain-boundary oxygen content, by control of oxidizing heat treatments and sintering additives, was found to result in a transition in fracture mechanism from transgranular to intergranular fracture, with an associated increase in fracture toughness. This phenomenon is correlated to an oxygen-induced change in grain-boundary chemistry that appears to affect fracture by ''weakening'' the interface, facilitating debonding and crack advance along the boundaries, and consequently toughening by grain bridging. It is concluded that if the oxygen content in the thin grain-boundary films exceeds a lower limit, which is {approx}0.87 equiv% oxygen content, then the interfacial structure and bonding characteristics favor intergranular debonding during crack propagation; otherwise, transgranular fracture ensues.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15014652
- Report Number(s):
- UCRL-CONF-208303; TRN: US200802%%1407
- Resource Relation:
- Journal Volume: 839; Conference: Presented at: 2004 MRS Fall Meeting, Boston, MA, United States, Nov 29 - Dec 03, 2004
- Country of Publication:
- United States
- Language:
- English
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