Synthesizing high α-phase Si3N4 powders containing sintering additives

Fine grain α-phase silicon nitride (Si3N4) ceramic powders were produced via carbothermic reduction of colloidal SiO2, which contained pre-mixed additives of sintering aids primarily consisting of oxides such as MgO and Y2O3. The powders that were pre-mixed in the starting reactants were chosen based on the final powder composition and on type and amount of the secondary phases desired for sintering. After synthesizing, powder properties were examined using standard characterization techniques (XRD, SEM, BET, etc). This technique of ceramic synthesis has advantages in providing nitride-based ceramic powders, which contain secondary in situ phases that are distributed as sintering additives. Silicon nitride ceramic powders synthesized using this method might therefore be readily sintered because the homogeneously distributed sintering additives were present in the starting materials. In this work, the processing parameters are described in terms of the synthesis conditions.