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An in-situ toughened Si_3N_4 ceramic is obtained by hot-pressing.Its flexural strength andfracture toughness are 960MPa,12.74MPa·m~(1/2)at room temperature and 720MPa,23.94MPa·m~_(1/2)at 1350℃,respectively.The relation between grain size of β-Si_3N_4 and mechanicalproperties is investigated.The glassy phase containing Y and La plays an important role inincreasing high-temperature mechanical properties because of its high viscosity and softeningtemperature.Crack deflection,crack branching and pullout of rodlike β-Si_3N_4 grains are ob-served in this material by SEM,and the toughening mechanisms are discussed.
An in-situ toughened Si_3N_4 ceramic is obtained by hot-pressing. Iz flexural strength and toughness are 960 MPa, 12.74 MPa · m ~ (1/2) at room temperature and 720 MPa, 23.94 MPa · m ~ _ (1/2) at 1350 ℃, respectively.The relation between grain size of β-Si_3N_4 and mechanical properties is investigated. Glassy phase containing Y and La plays an important role inincreasing high-temperature mechanical properties because of its high viscosity and softeningtemperature .Crack deflection, crack branching and pullout of rodlike β-Si_3N_4 grains are ob-served in this material by SEM, and the toughening mechanisms are discussed.