Electromechanical and ferroelectric properties of (Bi_1/2Na _1/2)TiO₃-(Bi_1/2K_1/2)TiO ₃- (Bi_1/2Li_1/2)TiO₃-BaTiO ₃ lead-free piezoelectric ceramics for accelerometer application

Lead-free (0.90-x)(Bi_1/2Na_1/2)TiO₃-0. 05(Bi_1/2K_1/2)TiO₃-x(Bi_1/2Li _1/2)TiO₃-0.05BaTiO₃ 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 (Bi _1/2Li_1/2)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 ε_r=785 and dissipation factor cosδ=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 °C to ∼ 136 °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.