Subgrain Microstructure in High-Performance BaTiO3 Piezoelectric Ceramics

We have successfully observed subgrains of 1 mu m average size in large grains (1 to 10 mu m) in high-performance barium titanate (BaTiO3) piezoelectric ceramics manufactured by two-step sintering. The BaTiO3 ceramics fabricated from hydrothermally synthesized BaTiO3 with an average particle size of 0.1 mu m 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. (C) 2008 The Japan Society of Applied Physics