Dense yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) +28 vol% alumina nanocomposite ceramics with and without 17 vol% oxynitride glass were fabricated at 1380degreesC using microwave sintering. The specimens were uniaxially compressed in the temperature range 1250 to 1400degreesC. Strain rates as high as 10(-4) (s(-1)) were measured at 1350degreesC and 90 MPa in the glass-free specimens with the stress exponent of 1.5. Similar strain rates were measured at lower compressive stresses in the counterpart glass-containing specimens. The stress exponent in the glass-containing specimens changed from 1.0 at 1250degreesC to 2.0 at higher temperatures. Dynamic grain growth of the alumina grains was inhibited in the presence of the oxynitride glass. Plastic deformation at lower temperatures in glass-containing alloy occurred by cooperative grain boundary sliding, aided by viscous flow of the grain boundary glassy phase. The changes in the deformation behavior at higher temperatures were related to crystallization of the glass and simultaneous plastic deformation by grain boundary sliding. (C) 2005 Springer Science + Business Media, Inc.