晶界相对半透明氮化铝陶瓷透过率的影响

分别添加质量分数为3%的CaF2和Y2O3为烧结助剂,在相同烧结工艺制度下采用放电等离子烧结(spark plasma sintering,SPS),制备了两种半透明AlN陶瓷.两种样品有相近的密实度和晶粒尺寸,但是它们的透过率却相差很大.用扫描电镜,X射线衍射分析和透射电镜结合能量散射型X射线光谱分析仪对样品微观结构进行分析.结果表明:晶界相的存在及分布方式对样品透过率有重要影响.添加CaF2的样品表现出很高的纯度,晶界及三角晶界处观察不到第二相.添加Y2O3的样品中,由于生成的晶界相Y3Al5O12沿AlN晶界分布,阻隔AlN晶粒之间的连接,在晶界处造成光散射,导致样品透过率下降.

EFFECT OF GRAIN BOUNDARY PHASE ON TRANSMITTANCE OF TRANSLUCENT AIN CERAMICS

Two kinds of translucent aluminum nitride (AlN) ceramics were prepared by the spark plasma sintering (SPS) under the same parameters with 3% (in mass) CaF_2 and Y_2O_3 as sintering additives. Microstructures were characterized using X-ray diffraction, scanning electron microscope(SEM) and transmission electron microscope(TEM). The sintered density and grain size of the two samples were fairly similar; however, the transmittances were quite different. Scanning electron microscope and TEM studies show that the grain boundary phase has a major influence on the transmittance. No secondary phases were observed at grain boundaries or triple-point junctions in the sample doped with CaF_2; however, the existence of formed Y_3Al_5O_ 12 along grain boundaries disrupted connections of AlN grains and caused great light scattering on the grain boundaries, resulting in a decrease in the transmittance of the sample doped with Y_2O_3.