The structure of transition fronts in barium titanate

The ferroelectric transition in barium titanate is first order, and can proceed by the passage of well-defined transition fronts across the crystal. The fronts are found to have an interesting double structure and this structure is studied by a number of methods. It is suggested that the region of the crystal lying between the two parts of the front has a structure which near the surfaces of the crystal is similar to that of the ferroelectric structure and in the centre of the crystal is similar to that of the cubic non-ferroelectric structure. From permittivity measurements, and from optical measurements, it is estimated that the surface structure occupies approximately one-quarter of the crystal thickness.