Enhancement of Si₃N₄ ceramics via evolution of grain interface between ZrO₂ and Si₃N₄ under pressureless sintering

Abstract

Silicon nitride (Si3N4) as a structural ceramic material, its strength, and toughness are the decisive characteristics of damage tolerance and reliability. In this work, Si3N4 ceramics is enhanced via evolution of grain interface between Si3N4 and ZrO2, which bending strength and fracture toughness reached 982.8 MPa and 9.81 MPa·m1/2, respectively. The interface evolution of the ZrO2 and Si3N4 grains were investigated via both first‐principles molecular dynamics simulation and experiment. The Si3N4/ZrO2 interface structure was observed by high‐resolution transmission electron microscopy, include: (i) glass phase film, (ii) Zr3N4 film. First‐principles molecular dynamics simulation reported here provide an atomic‐level description of the formation mechanisms of the interface structure. The Si‐O bond and Zr‐N bond was formed to provide the Si3N4/ZrO2 interface bond. Moreover, the embedded‐like composite structure between Si3N4 and ZrO2 was formed during the sintering process, which can deflect cracks and result in an increase in the fracture energy. Due to the strength difference of Si3N4 and ZrO2, cracks tend to propagate through the grains of ZrO2 and deflects when it encounters the rod‐like Si3N4 grains. In the same time, the ZrO2 plays a role with respect to refinement of the β‐Si3N4 grain size and decrease of the glass phase content.

The explanation of electrical properties changes under NH3 and H2 containing atmospheres in risen temperatures of ceria- and zirconia-based solid electrolytes by means of electrochemical impedance spectroscopy

“…The most popular method to achieve this aim is the addition of a precisely adjusted amount of divalent or trivalent metal atoms. The following compounds have been reported as ZrO 2 dopants: CaO, MgO, Y 2 O 3 , Sc 2 O 3 , Al 2 O 3 , Si 3 N 4 , AlN, CuO [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Such modi cation has a direct effect on the considerable rise of the speci c electrical conductivity.…”