Effect of grain size on the electrical properties of high dense BPT nanocrystalline ferroelectric ceramics

Nanosized Ba0.8Pb0.2TiO3 powders obtained by high energy ball milling were compacted and sintered into nanocrystalline ferroelectric ceramics using spark plasma sintering (SPS). The prepared ceramic samples were characterized by field emission scanning electron microscopy, X-ray diffraction, and electrical property measurements. All the samples show a density over 97% of the theoretical value and an average grain size of ∼60–200 nm depending on the ball milling time. The dielectric data exhibit a ferroelectric–paraelectric phase transition and a maximum relative permittivity of 19,000 at 225 °C and 100 kHz at the average grain size of ∼60 nm. The values of the dielectric constants both at room temperature and at the phase transition temperature increase considerably as the average grain size decreases. The remanent polarization and coercive field strength decrease slightly as the average grain size decreases but remain at an acceptable level for ferroelectric applications.