Abstract
A single-phase alumina ceramic with elongated grains was obtained by pressureless sintering of alumina powder at 1500 °C nitrogen gas, using YSiAlON oxynitride glass as a sintering additive. The green compacts were sintered for various times to determine the optimal conditions for liquid-phase sintering of alumina with a YSiAlON glass additive. The relative densities of samples sintered at 1500 °C for 3 h reached as high as 99.2%, but further increasing the holding time resulted in decreased densities. X-ray diffractometry (XRD) and transmission electron microscopy (TEM) with energy-dispersive analysis indicated a Y 3Al 5O 12 crystalline phase and a small amount of amorphous phase, containing nitrogen and oxygen, at the grain junctions. The high-temperature mechanical properties of A1 2O 3/5 wt.%YSiAlON ceramic are much higher than monolithic alumina. The bending strength and fracture of the materials at 800 °C were 420±17 MPa and 5.3±0.2 MPa m 1/2, respectively. The YSiAlON additive was found to be useful for the liquid-phase sintering of alumina.
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