INTERNAL-FRICTION OF CERAMIC SINGLE-CRYSTALS AT VERY HIGH-TEMPERATURE

Low-frequency internal friction behavior has been investigated in nomi nally pure MgO single crystal, sapphire single crystal, and two ruby c rystals containing different amounts of solute chromium. Internal fric tion data were collected with the crystals oriented for primary slip t o occur. The measurement temperature was raised to temperatures very c lose to the respective melting points of the ceramic crystals and damp ing data collected by means of a recently developed torsion pendulum e nabling measurement of damping characteristics at very high temperatur es. In light of the internal friction data available up to approximate to 2500 degrees C, both as a function of frequency and temperature, s ome fundamental aspects of dislocation motion in ceramic crystals coul d be characterized and their relation to the damping behavior clarifie d. [S0163-1829(98)03042-2].