Electromechanical and ferroelectric properties of (Bi1/2Na1/2)TiO3-(Bi1/2K1/2)TiO3-(Bi1/2Li1/2)TiO3-BaTiO3 lead-free piezoelectric ceramics for accelerometer application

Lead-free (0.90-x)(Bi1/2Na1/2)TiO3-0.05(Bi1/2K1/2)TiO3-x(Bi1/2Li1/2)TiO3-0.05BaTiO(3) piezoelectric ceramics (abbreviated as BNKLBT-100x, with x ranged from 0 to 2.5 mol%) were prepared by a conventional mixed oxide method. Effects of the amount of (Bi1/2Li1/2)TiO3 (BLT) on the electrical properties and crystal structure of the BNKLBT ceramics were examined. BNKLBT-1.5 ceramics have good properties with piezoelectric constant d(33)=163 pC/N, electromechanical coupling factor k(p)=0.33, k(t)=0.53, relative permittivity epsilon(r)=785 and dissipation factor cos delta=2.2% at 1 kHz. The sample has larger remnant polarization than BNKLBT-0 ceramics and the same coercive field as BNKLBT-0 ceramics. X-ray diffraction analysis shows that the incorporated BLT diffuses into the BNT-BKT-BT lattice to form a solid solution during sintering, but changes the crystal structure from rhombohedral to tetragonal symmetry at higher BLT amounts. Depolarization temperature (T-d) of the BNKLBT-100x ceramics increases from 102 degrees C to similar to 136 degrees C for BNKLBT-0 to BNKLBT-2.5. BNKLBT-1.5 is used as the transduction element in compressive type accelerometer and its sensitivity is calibrated by the back-to back method. Within the +/- 2.5% tolerance, the lead-free accelerometer has a mean value of 2.97 pC/ms(-2) within 50 Hz-12.45 kHz and the lead-based accelerometer has a mean value of 4.34 pC/ms(-2) within 50 Hz to 8.24 kHz.