The Emergence of Intergranular Precipitates in TiO2‐Doped α‐Al2O3 Ceramics

The minor phase accumulated at intergranular regions in ceramics is usually associated with the global doping level of additives; however, such simplification often undermines the local variation in liquid composition that leads to the emergence of precipitation. In this paper the correlation between precipitation and intergranular liquid was investigated in a TiO 2 ‐doped Al 2 O 3 ceramic system. The discrepancy between XRD and SEM in detection of the intergranular Al 2 TiO 5 phase was rationalized by their difference in sensitivity that corresponds to a change from the casual to general mode of local liquid variation. Analytical TEM in addition revealed Ti‐rich nanoprecipitates aligning along grain boundary (GB). The two intergranular phases were associated with separate processes of intergranular liquid, as clarified via a representative case that exhibited the extra grain growth from annealing. The nanoprecipitates were created from a binary liquid in local equilibration with segregation to GB, which served as transporting routes to form ternary liquid at the multigrain junctions to initiate the main intergranular phase Al 2 TiO 5 .