Lead zirconate titanate thick films by sol-gel method for piezoelectric applications

Lead zirconate titanate (PZT) films were fabricated by a sol-gel method. The sol was prepared using Ti(OⁱPr)₄, Pb(OAc)₂·3H₂O, Zr(OⁿBu)₄, and diethanolamine (DEA) with a molar ratio of DEA/(Ti+Zr)=1. They were dissolved in isopropanol solvent. The concentrations of the sol were about 1.5 and 0.4 mol/L with compositions of Pb_x(Ti_0.5Zr_0.5)O₃, (x = 1.1 and 1.3). The substrate used was Si wafer sputtered with Pt as an electrode. The deposition was conducted by a dip-coating procedure. After deposition and drying at 110°C, the substrate was heated at 700°C for 30min to crystallize perovskite phase. This coating-drying-heating cycle was repeated several times to obtain a thick PZT film. The fabricated films was about 7 μm thick by eight depositions and consisted of the first three thin layers (90 nm each) and five to eight thick layers (1.2 μm each). The dielectric constant of the films was about 400 and tanδ was about 0.01 at 1 kHz. The films exhibited typical ferroelectric P-E hysteresis curve and the remanent polarization and coercive force were 29.7 μC/cm² and 69.7 kV/cm, respectively. The admittance measurement of the poled thick film exhibited clear resonance and antiresonance peaks. The piezoelectric displacement was measured by a laser interferometer and the piezoelectric constant, d₃₃, was calculated as 430 to 550 pm/V.