Effects of sintering additives on dielectric breakdown strength of sintered reaction-bonded silicon nitride.

We prepared sintered reaction-bonded silicon nitride (Si 3 N 4) by using various lanthanide oxides and magnesia for sintering additives and evaluated their effects on the microstructure and dielectric breakdown strength (DBS). Both the microstructure and DBS varied by the types of the sintering additives, and artificial intelligence (AI) based determination was conducted for the DBS to separate the effect of microstructural factors from that of sintering additives. The results indicated that the DBS values varied mainly by the former effect. The microstructures of Si 3 N 4 with Eu 2 O 3 and La 2 O 3 contained a large number of pores, leading to lowered DBS; on the contrary, those with Tm 2 O 3 and Y 2 O 3 possessed dense microstructures with large-elongated grains, showing higher DBS. On the other hand, the Si 3 N 4 with Yb 2 O 3 showed lower DBS than what AI-determined from the microstructures because the additive forms grain boundary phase with a low electrical resistance. [ABSTRACT FROM AUTHOR]