It's a very new field in ferroelectricity (part of condensed matter physics), wurtzite ferroelectrics are very peculiar because they are inherently polar and exhibit no phase transition (to my knowledge) contrary to archetypal ferroelectrics such as BaTiO3, PbTiO3 etc. Pure AlN is not ferroelectric however if it is alloyed with elements such as Scandium, Boron etc. Polarization becomes switchable ! The explanation is mainly involving bond ionicity/softness (incorporating Sc atoms create softer bonds) as well as structural distortions. Contrary to perovskites, polarization is only along +c so no ferroelastic domains can be expected because there are only two directions that are equivalent From what we know so far wurtzite nitrides exhibit completely new phenomena not observed in any other ferroelectric : - The switching occurs along atomic columns, it is also stochastic giving rises to rough DWs (would be interesting to calculate the scaling exponents !) - If you switch a Sc-doped AlN thin film in a…