High piezoelectric properties of BaTiO3–xLiF ceramics sintered at low temperatures

BaTiO3–xLiF ceramics were prepared by a conventional sintering method using BaTiO3 powder about 100 nm in diameter. The effects of LiF content (x) and sintering temperature on density, crystalline structure and electrical properties were investigated. A phase transition from tetragonal to orthorhombic symmetry appeared as sintering temperatures were raised from 1100 °C to 1200 °C or as LiF was added from 0 mol% to 3 mol%. BaTiO3–6 mol% LiF ceramic sintered at 1000 °C exhibited a high relative density of 95.5%, which was comparable to that for pure BaTiO3 sintered at 1250 °C. BaTiO3–4 mol% LiF ceramic sintered at 1100 °C exhibited excellent properties with a piezoelectric constant d33 = 270 pC/N and a planar electromechanical coupling coefficient kp = 45%, because it is close to the phase transition point in addition to high density.