Piezoelectric Effect Induced By DC Bias In PLZT And PBZT Relaxor Ferroelectric Ceramics

Temperature dependence of dielectric constant (K)(33)-T) , transverse field-induced strain (x₂-E) and hysteresis loops were studied for strontium , bismuth , lanthanum , niobium-doped barium-modified lead zirconate titanate (PBZT) and niobium , barium-doped lanthanum lead zirconate titanate (PLZT) relaxor ferroelectric ceramics . Dielectric constant K₃₃ , planar electromechanical coupling factor k_p , elastic compliance S₁₁^E and effective piezoelectric coefficient d₃₁ under dc bias and their temperature dependences were studied for these materials. The experiments show that the effective piezoelectric coefficient d₃₁ of modified PBZT and PLZT relaxor ferroelectric ceramics can be controlled by dc bias and its temperature dependence is much less than that of 0.9PMN-0.1PT ceramic . Average Curie temperature T_av shifts toward lower temperature , temperature dependences of dielectric constant and piezoelectric coefficient d₃₁ under dc bias decrease, transverse field-induced strain and electric polarization at the same field decrease as the Ba or Nb content increases for modified PLZT and PBZT compositions . Dielectric constant and piezoelectric coefficient d₃₁ under the same bias field increase with temperature in the range of 10-50℃ for all compositions . Dielectric constant increases with dc bias at first and then decreases with increasing dc bias at the same temperature for all compositions . Planar electromechanical coupling factor k_p increases with dc bias at first and saturates at a certain bias field for all compositions. The |d₃₁| value increases with dc bias at first and reaches to a maximum , after that it decreases with increasing bias field at the same temperature for all compositions . For all compositions, K₃₃ and |d₃₁| under10Kv/cm dc bias increase with temperature and reach to maximum , then decrease with increasing temperature , |d₃₁| reaches to a maximum at lower temperature . k_p under 10Kv/cm dc bias is almost temperature independent at first then decreases with temperature . Dielectric and piezoelectric characteristics at dynamic and dc bias state were studied for 3mol% barium-...