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

Abstract

Lead zirconate titanate (PZT) films were fabricated by a sol-gel method. The sol was prepared using Ti(O/sup i/Pr)/sub 4/, Pb(OAc)/sub 2//spl middot/3H/sub 2/O, Zr(O/sup n/Bu)/sub 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/sub x/(Ti/sub 0.5/Zr/sub 0.5/)O/sub 3/, (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/spl deg/C, the substrate was heated at 700/spl deg/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 /spl mu/m thick by eight depositions and consisted of the first three thin layers (90 nm each) and five to eight thick layers (1.2 /spl mu/m each). The dielectric constant of the films was about 400 and tan/spl delta/ 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 /spl mu/C/cm/sup 2/ 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, d/sub 33/, was calculated as 430 to 550 pm/V.