Electromechanical and ferroelectric properties of(Bi_(1/2)Na_(1/2))TiO_3-(Bi_(1/2)K_(1/2))TiO_3-(Bi_(1/2)Li_(1/2))TiO_3-BaTiO_3 lead-free piezoelectric ceramics for accelerometer application

摘要

Lead-free (0.90 - x)(Bi_(1/2)Na_(1/2))TiO_3-0.05(Bi_(1/2)K_(1/2))TiO_3-x(Bi_(1/2)Li_(1/2))TiO_3-0.05BaTiO_3 piezoelectric ceramics (abbreviated as BNKLBT-l00x, with x ranged from 0 to 2.5 mol %) were prepared by a conventional mixed oxide method. Effects of the amount of (Bi_(1/2)Li_(1/2))TiO_3 (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 tan δ = 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 ℃ to ～ 136 ℃ 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.