Ferroelectricity and dipole-dipole interactions in NH4TiOF3 mesocrystals

We report the discovery of ferroelectricity in NH4TiOF3 by piezoresponse force microscopy (PFM) technique and first principles calculations. The first principles calculations show that the O has an in-plane site preference in the layered structure of this material and the energetics favor a ferroelectric ground state with a calculated polarization of approximately 8 μC/cm2. Lateral and vertical PFM results show stable ferroelectricity at ambient temperature. The ferroelectricity is first observed for mesocrystals. It also provides an explanation for observations of mesocrystal growth even in the absence of surfactants since electric dipolar interactions can guide self-assembly.