Singular grain boundaries in alumina doped with silica

Abstract

Pure Al2O3 powder compact sintered at 1400degreesC after adding 100 mol ppm of SiO2 shows grain boundaries that are flat, even across the triple junctions. TEM observations show that these flat grain boundaries are parallel to the basal planes of the grains on one side. These flat grain boundaries must be singular. At such a low SiO2 concentration and a low temperature, it is very unlikely that any liquid phase is present at these grain boundaries to cause such flat boundary shapes.