Dielectric and electromechanical properties of LiNbO3-modified (BiNa)TiO3-(BaCa)TiO3 lead-free piezoceramics

The dielectric and electromechanical properties of LiNbO3-modified (1-x) [0.91Na(0.5)Bi(0.5)TiO(3)-0.09Ba(0.70)Ca(0.30)TiO(3)]-xLiNbO(3) (abbreviated as (BiNa) TiO3-(BaCa) TiO3-LN) lead-free piezoceramics were investigated. The electrical properties revealed that the addition of LiNbO3 (LN) induces a phase transition from a non-ergodic relaxor to an ergodic relaxor in the (BiNa) TiO3-(BaCa) TiO3-LN system. A large electrostrain of similar to 0.418% with a normalized strain of similar to 690 pm V-1 at 6 kV mm(-1) was observed at the coexistence of the non-ergodic relaxor and ergodic relaxor phases for LN 0.020, where a field-assisted reversible phase transition between metastable ferroelectric and stable ergodic relaxor phases occurs. Subsequently, a gradual enhancement in the temperature stability of the dielectric constant was observed. At 3 mol.% LN, a nearly constant temperature and a frequency-invariant permittivity of er similar to 3300 over a broad temperature range of 147 degrees C-306 degrees C was observed along with small losses from room temperature up to 400 degrees C.