Despite of their small volume fraction, the grain boundaries in functional ceramics have a huge influence on the properties. This influence depends on the thermal history of the ceramic part as the volume fraction of the boundaries can be changed by orders of magnitude during processing due to the microstructural evolution. Both aspects are closely linked as tailoring of one of the properties linked to the grain boundaries, growth kinetics or dielectrical properties, changes the other one.
Every polykristalline material shows the effect that at sufficiently high temperatures the ist microstructure coarsens. The energy of the system is reduced by the reduction of the stored boundary energy.
A spezial focus of the research at the IKM is abnormal grain growth, an effect where a small number of grains growths much faster than the majority. After a certain period of time the small grains will be completely consumed resulting in normal growth behaviour on a different length scale (Picture: abnormal growth in BaTiO3). This type of microstructural evolution is impossible under the assumption that the mobility and the energy of the different grain boundaries are homogeneous.