Alignment of defect dipoles in polycrystalline ferroelectrics

Using electron paramagnetic resonance (EPR), we show the alignment of defect dipoles along the direction of the spontaneous polarization in polycrystalline BaTiO3 ceramics by subjecting the capacitors to a dc bias at elevated temperatures. The alignment is demonstrated to occur via orientation dependent EPR signals in the polycrystalline perovskite lattice. The alignment of the defect dipoles is found to strongly enhance the light sensitivity of the defects. This observation may have important implications for photorefractive applications.