| Abstract Scope |
While interfaces must be in equilibrium with at least one bulk phase, they have structures and properties that may not be observed in the bulk under any thermodynamic constraints. Further, the interface layer, as defined by Cahn, must contain all gradients in order to apply interface thermodynamics. In ferroelectrics, grain boundaries are distinct from domain walls because they are characterised by both crystallographic and polarisation misorientations. Here a critical point wetting analysis of tilt grain boundaries in tetragonal ferroelectrics is presented and transitions in grain boundary core order and polarization are identified. While previous authors have been inspired by Cahn’s original critical point wetting analysis, this is the first application to vector fields, where the bulk and grain boundary core contributions to energetics are both a function of the misorientations. Implications for microstructural evolution as a function of temperature are drawn for both ceramic oxide and organic perovskite materials. |