Effects of niobium doping on the piezoelectric properties of sol-gel-derived lead-zirconate-titanate films

Sol-gel-derived lead-zirconate-titanate (PZT) films doped with various amounts of niobium (Nb) have been spin coated on silicone substrates, and their remanent polarization P-r, and effective longitudinal and transverse piezoelectric coefficients (d(33,c) and e(31,c)) as well as the pyroelectric coefficient p, have been measured. The Zr/Ti ratio of the films is 53/47. Our results reveal that the Nb-dopant effects on the PZT films are very similar to the experimentally known effects on the corresponding bulk ceramics, i.e., enhancing both the longitudinal and transverse piezoelectric properties. However, because of the substrate clamping effect, the exact enhancement in the longitudinal piezoelectric properties cannot be evaluated by the d(33,c) measurement on the film samples. Accordingly, the observed d(33,c) value of the Nb-doped PZT films remains almost unchanged while the observed -e(31,c) (as well as P-r and p) increases with increasing Nb concentration, showing an optimum Nb concentration of 2 mol %. For the PZT film doped with 2% Nb, the observed values of P-r, d(33,c), -e(31,c), and p are about 30 muC/cm(2), 95 pm/V, 18 C/m2, and 350 muC/m(2) K, respectively. (C) 2004 American Institute of Physics.