Thermally-induced grain boundary grooving has typically been characterized
experimentally by either (1) optical interferometry (OI) or (2) reference line (RL)
technique. For the OI technique, groove angle and groove width are reported and for
the RL technique, groove angle, width and depth are reported. Even recent Atomic Force
Microscope (AFM) studies of grain boundary grooving report their results in terms of
groove angle, width, and depth exclusively. These measurements have been interpreted
in terms of Mullins' 1957 theory on grain boundary grooving, which includes a
derivation of the grain boundary groove profile. However, analyzing the groove depth,
width, and angle uses only a small fraction of the groove profile information provided
by Mullins' theory. In contrast to the literature, this study uses AFM data from thermal
grooving in polycrystalline alumina to make a detailed comparison between
Mullins' equation (and a modified form of Mullins' equation) for the entire groove
profile rather than just the groove width or groove angle, thus providing a more
rigorous and comprehensive test of theory. In addition, despite the wider and deeper
grooves produced by microwave annealing, the modified form of Mullins' equation fits
well both the microwave and conventionally annealed groove profiles.