Thermally induced structural changes in incommensurate calcium barium niobate Ca0.28Ba0.72Nb2O6 (CBN28)

► The incommensurate structure of relaxor ferroelectric CBN28 was refined at high temperatures. ► The modulations consist of a wave-like occupation of cation sites and displacements of the O atoms. ► The modulations survive the ferroelectric phase transition and no change of symmetry was found. ► Atomic shifts of the ions and the corresponding electric polarization do not completely vanish. ► Thermal motions lead to a cross-over from parallel to anti-parallel configuration of Nb atoms.