Mechanism for the development of anisotropic grain boundary character distributions during normal grain growth

Grain boundaries in polycrystalline magnesia-doped alumina and yttrium aluminum garnet were classified as growing in area or shrinking in area on the basis of topology and curvature considerations. Measurements of dihedral angles at grain boundary thermal grooves were used to determine that the energies of the growing boundaries are, on average, lower than the energies of the shrinking boundaries. The observations also show that the length of a boundary is inversely correlated to its energy. The findings suggest that anisotropic grain boundary character distributions, which influence the properties of polycrystals, develop because higher-energy grain boundaries are preferentially eliminated from the network during grain growth.