Local electric-field-driven repoling reflected in the ferroelectric polarization of Ce-doped Sr0.61Ba0.39Nb2O6

We present pyroelectric measurements with the relaxor-ferroelectric strontium barium niobate in the phase transition regime. It is demonstrated that domains poled at high temperatures are more stable than those oriented at room temperature. This yields a higher phase-transition temperature when heating the sample and a strong repoling during the cooling process. We explain this difference within the framework of the random field model for relaxor ferroelectrics.