Ferroelectric properties of dense nanocrystalline BaTiO3 ceramics

Dense BaTiO3 ceramics with 50 nm average grain size obtained by spark plasma sintering were investigated. The dielectric data show a broad ferro-para phase transition with a maximum permittivity of ~1100 at 390 K and 1 kHz. The local ferroelectric switching behaviour was investigated by piezoresponse force microscopy. Typical piezoelectric hysteresis loops were recorded at different positions of the sample. The present results provide experimental evidence for polarization switching at the local scale, indicating that the critical grain size for the disappearance of ferroelectric behaviour in dense, bulk BaTiO3 nanocrystalline ceramics is below 50 nm.