Low-frequency internal friction behavior has been investigated in nominally pure MgO single crystal, sapphire single crystal, and two ruby crystals containing different amounts of solute chromium. Internal friction data were collected with the crystals oriented for primary slip to occur. The measurement temperature was raised to temperatures very close to the respective melting points of the ceramic crystals and damping data collected by means of a recently developed torsion pendulum enabling measurement of damping characteristics at very high temperatures. In light of the internal friction data available up to ≈2500 °C, both as a function of frequency and temperature, some fundamental aspects of dislocation motion in ceramic crystals could be characterized and their relation to the damping behavior clarified.

• Received 13 March 1998

DOI:https://doi.org/10.1103/PhysRevB.58.11880