Wulff's relationship of ruby single crystals grown from molybdenum trioxide flux studied by contact angles of liquid droplets

The contact angles of water and formamide droplets on two different ruby crystals grown from MoO3 flux were measured. The specific surface free energies of the (1 1 2¯ 3), (1 0 1¯ 3), and (0 0 0 1) faces were calculated using the Fowkes approximation and compared with the length of the normal lines from the center to the crystal faces. The relationship between the specific surface free energy and the morphology of each crystal is found to satisfy Wulff's relationship.