The variation of piezoelectric and electrostrictive strain as a function of frequency and applied electric field using an interferometric technique

A Zygo laser interferometer system has been used to measure the strain induced in piezoelectric lead zirconate titanate (PZT) and electrostrictive lead magnesium niobate (PMN) based ceramics. The piezoelectric coefficients d₃₃, d₃₁ and d₁₅ of PZT ceramics have been determined as a function of electric field and frequency. The strain and polarization of PMN-PT ceramics have been measured at AC fields of up to 4 MV/m. For PMN-based ceramics, the results suggest that a quadratic relation of strain with polarization (S = Q·P²) is not valid at high electric fields and higher order terms must be considered. DC bias measurements at room temperature showed that the maximum d₃₃ of PMN-15 ceramics was 800 pm/V at the bias field of 0.67 MV/m and had little frequency dependence in the frequency range from 1 Hz up to 2.5 kHz. However, PMN-38 ceramic, with a maximum d₃₃ of 1200 pm/V at the bias field of 0.43 MV/m, showed frequency dependence from 1 Hz up to 2.5 kHz.