Fabrication and properties of pressure-sintered reaction-bonded Si3N4 ceramics with addition of Eu2O3-MgO-Y2O3

Dense pressure-sintered reaction-bonded Si3N4 (PSRBSN) ceramics were obtained by a hot-press sintering method. Precursor Si powders were prepared with Eu2O3-MgO-Y2O3 sintering additive. The addition of Eu2O3-MgO-Y2O3 was shown to promote full nitridation of the Si powder. The nitrided Si3N4 particles had an equiaxial morphology, without whisker formation, after the Si powders doped with Eu2O3-MgO-Y2O3 were nitrided at 1400 degrees C for 2 h. After hot pressing, the relative density, Vickers hardness, flexural strength, and fracture toughness of the PSRBSN ceramics, with 5 wt% Eu2O3 doping, were 98.3 +/- 0.2%, 17.8 +/- 0.8 GPa, 697.0 +/- 67.0 MPa, and 7.3 +/- 0.3 MPa m(1/2), respectively. The thermal conductivity was 73.6 +/- 0.2 W m(-1) K-1, significantly higher than the counterpart without Eu2O3 doping, or with ZrO2 doping by conventional methods.