Effect of processing conditions on the piezoelectric properties of sol-gel derived Pb(Zr,Ti)O₃ films for micromechanical applications

Lead zirconate titanate (PZT) films of composition close to the morphotropic phase boundary were deposited onto standard Si/SiO₂/Ti/Pt substrates using a modified sol-gel process. The preparation conditions were optimized to obtain high-quality films at sufficiently Iow temperature (T_a = 500 °C). The dielectric, ferroelectric, and piezoelectric properties of the films were then measured as a function of the annealing temperature and the number of distillations to evaluate their suitability for micromechanical applications. The maximum values of the longitudinal charge and voltage piezoelectric coefficients were d₃₃ ∼ 65 pm/V and g₃₃ ∼ 4 × 10^-3 Vm/N, respectively. The results indicate that the piezoelectric properties improved and became saturated with increasing number of distillations and are almost independent on T_a. Only moderate decrease of the piezoelectric response with frequency suggests that the investigated PZT films can be used in high-frequency piezoelectric applications. The results are discussed in terms of the microstructure and interface effects on the piezoelectric deformation in ferroelectric thin films.