粉料表面氧含量对GPS烧结氮化硅陶瓷显微结构的影响

Effect of Powder Surface Oxygen Content on Microstructure of GPS Silicon Nitride Ceramics

通过研究 GPS 烧结氮化硅陶瓷的室温和高温抗弯强度、晶界相含量和成分以及晶界析晶相随氮化硅粉料表面氧含量的变化规律,发现当粉料表面氧含量低于 1.35 mg/m2时,氮化硅陶瓷在室温下的抗弯强度基本保持不变。试样在 1200℃时的抗弯强度明显低于室温强度,且随着粉料表面氧含量的增加有一最高值。由于烧结助剂引入的 O 和 Si 在烧结过程中的还原气氛下发生反应而损失,烧结体中晶界相的实际含量显著低于粉料中烧结助剂的加入量。随粉料表面氧含量的增加,氮化硅陶瓷烧结体中的二次析晶相 α-Y2Si2O7和 β-Y2Si2O7消失,只有 β-Si3N4晶相和晶界玻璃相存在。

For Y2O3 -Al2O3-containing GPS silicon nitride ceramics, the effect of powder surface oxygen concentration on flexural strength, intergranular chemistry, and devitrification phase was studied comprehensively Room-temperature strength of the sintered samples remains nearly invariant in quite a large range of the surface oxygen content, while high-temperature flexural strength at 1 200degreesC is maximized when the surface oxygen content is adjusted to a certain value, under which condition the composition of the intergranular phase contains high content of N and the highest atomic ratio of N:Si. Because of the reactive consumption of intergranular oxygen and silicon in reducing atmosphere during densification, the measured content of total intergranular phase is less than the expected value. With the increasing oxygen content on powder surface the devitrification phase a and beta-Y2Si2O7 will gradually disappear from the sintering body where beta-Si3N4 and intergranular glass phase exit only.