Studying Trapped Grains in Alumina using SEM and EBSD

Despite development of high-resolution [1] and in situ [2] microscopies, grain boundaries remain something of an enigma, especially in ceramic materials where second-phase glass is often found to be present as films or precipitates in the interfacial regions. The glass is an unavoidable product in the liquid-phase sintering (LPS) process and incorporates intentional additives and accidental impurities. [3-4] Abnormal grain growth (AGG) has been associated with second-phase dissolution rather than defect or pore coalescence. [5-6] The number of crystal defects inside the polycrystalline material may dictate which of the grains will grow and which will be consumed. [5] Crystal anisotropy will promote orientation-dependent lattice diffusion of solutes, which may result in an induced strain energy within the crystal. [7] The solutes will lower the strain energy by sitting at the spacious boundaries rather than in the grain matrix.