Subgrain Microstructure in High-Performance BaTiO3Piezoelectric Ceramics

We have successfully observed subgrains of 1 µm average size in large grains (1 to 10 µm) in high-performance barium titanate (BaTiO 3 ) piezoelectric ceramics manufactured by two-step sintering. The BaTiO 3 ceramics fabricated from hydrothermally synthesized BaTiO 3 with an average particle size of 0.1 µm had a density = 5.93 g/cm 3 , an electromechanical coupling factor k p = 50%, and a piezoelectric constant d 33 = 500 pC/N, which are the highest values reported thus far. Subgrain boundaries were considered to have a lower energy than main-grain boundaries. The subgrain structure restricted ferroelectric domain growth resulting in a nanosized domain structure, a large k p and a large d 33 . These features have important practical implications in addition to the scientific interest they generate in the fabrication of lead-free high-performance piezoelectric ceramics.