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

Abstract

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[sub r], and effective longitudinal and transverse piezoelectric coefficients (d[sub 33,c] and e[sub 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[sub 33,c] measurement on the film samples. Accordingly, the observed d[sub 33,c] value of the Nb-doped PZT films remains almost unchanged while the observed -e[sub 31,c] (as well as P[sub 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[sub r], d[sub 33,c], -e[sub 31,c], and p are about 30 µC/cm², 95 pm/V, 18 C/m², and 350 µC/m²K, respectively.