Abstract
A variety of combinations of YF3 and MgF2 were used as sintering aids in the fabrication of Si3N4 ceramics via gas pressure sintering (GPS). The synergistic effects of YF3 and MgF2 on the liquid viscosity, mechanical properties, thermal conductivities, and grain growth kinetics of the Si3N4 ceramics were investigated. The results showed that appropriately adjusting the YF3/MgF2 ratio could decrease liquid viscosity, reducing the diffusion energy barrier of the solute atom and promoting mass transfer. Meanwhile, the chemical bonding strength in the grain boundary complexions formed by the metal cations also influenced grain boundary migration. Samples doped with 4 mol% YF3 and 2 mol% MgF2 achieved the lowest grain growth exponent (n = 2.9) and growth activation energy (Q = 616.7 ± 16.5 kJ mol−1) as well as the highest thermal conductivity (83 W m−1 K−1) and fracture toughness (8.82 ± 0.13 MPa m1/2).
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