Measuring the Influence of Grain-Boundary Misorientation on Thermal Groove Geometry in Ceramic Polycrystals

We have used electron backscattered diffraction patterns to determine the misorientation of 201 adjacent pairs of grains in a magnesia polycrystal. The width and depth of the thermal grooves formed by these same grain boundaries were also measured by atomic force microscopy (AFM). By simulating the errors associated with the AFM observations and comparing our observations to existing data for magnesia and alumina, we show that, under appropriate experimental conditions, surface dihedral angles, relative grain-boundary energies, and surface diffusivities determined from AFM measurements are consistent with data acquired by more laborious techniques. Correlation of the grain-boundary misorientation and thermal groove geometry leads to the observation that grain boundaries with small misorientations, regardless of the rotation axis, have shallow thermal grooves and relatively low grain-boundary energies. Furthermore, numerous boundaries with relatively large misorientations but shallow thermal grooves correspond to special boundaries near coincident-sitelattice (CSL) misorientations. Finally, the data set indicates that factors other than the boundary misorientation, such as anisotropy of the surface energy and the grain-boundary tangent plane, play a role in determining the groove geometry.