Grain Size Effect on Dielectric, Piezoelectric and Ferroelectric Property of BaTiO3 Ceramics with Fine Grains

A series of highly dense barium titanate (BaTiO3) ceramics with average grain size ranging from 0.25 mu m to 10.15 mu m were prepared by either conventional sintering or a two-step sintering method, using ultrafine BaTiO3 powders prepared by hydrothermal approach. The impact of grain size on dielectric, piezoelectric and ferroelectric properties of BaTiO3 ceramics was investigated. Results indicate that the tetragonal phase of BaTiO3 ceramics increases with the increase of grain size. When the averaged grain size is above 1 mu m, the relative dielec-tric constant (epsilon') and piezoelectric coefficient (d(33)) at room temperature increase firstly with the decrease of grain size, with the maximum values of 5628 and 279 pC/N, respectively, at the grain size of 1.12 mu m, and then decrease rapidly with further decrease of the grain size. The remanent polarization P(r)of BaTiO3 ceramics rises with the in-crease of grain size, but the coercive field E-c exhibits opposite tendency. The variation of dielectric and piezoelec-tric properties resulted from the change of grain size is regarded as the impact of 90 degrees domain size and the number of the gram boundaries, while the change of hysteresis loops is due to the change of the crystal field in the grains and the "pinning" effect of the surface layer on the grains.