Grain boundary complexions: The interplay of premelting, prewetting, and multilayer adsorption

A thermodynamic model for coupled adsorption and disordering transitions at grain boundaries is developed by combining diffuse-interface and lattice-gas models and incorporating colloidal type interfacial forces. This model produces a systematical spectrum of interfacial phenomena for grain boundaries, including first-order and continuous coupled prewetting and premelting transitions, critical points, multilayer adsorption, layering and roughening, and complete wetting and drying, and it produces a series of grain boundary “phases” (complexions) with character similar to those observed by [Dillon et al., Acta Mater. 55, 6208 (2007)]. The presence of dispersion and electrostatic forces in ceramic materials can appreciably change grain boundary transitions.