Effect of nano-sized sintering additives on microstructure and mechanical properties of Si3N4 ceramics.

Abstract Nano-sized sintering additives such as MgO, Al 2 O 3 , Y 2 O 3 and La 2 O 3 are added to process Si 3 N 4 based ceramics. The effects of such sintering additives on the phase transformation, mechanical properties and microstructure of silicon nitride were investigated. XRD analysis of sintered silicon nitride with these sintering additives have shown the complete transformation of α-Si 3 N 4 into β-Si 3 N 4. The silicon nitride ceramics sintered with nano-sized additives (4MgO-4Al 2 O 3 –5La 2 O 3) have exhibited the highest fracture toughness. This is not only due to the weak glass|grain interface but also due to the formation of high aspect ratio grains (β-Si 3 N 4). Superior mechanical properties of Si 3 N 4 can be obtained by way of adding small and large RE3+ radii RE 2 O 3 (Y 2 O 3 and La 2 O 3) together than the addition of single RE 2 O 3. [ABSTRACT FROM AUTHOR]