Effect of niobium modifications to PZT (53/47) thin films made by a sol-gel route

Niobium-modified lead zirconate titanate thin films (PNZT) with nominal compositions, Pb(1-0.5x) (Zr0.53Ti0.47)(1-x) NbxO3:x=0.02-0.07, have been prepared using a diol based sol-gel route. Single-layer (0.5 mum) films were fabricated on platinised silicon substrates by spin-coating. The effect of niobium additions with regard to phase development, microstructure, and ferroelectric and dielectric properties were investigated for different annealing temperatures. For comparison, unmodified PZT films were also prepared. Niobium substitution increased the crystallisation temperatures for perovskite PNZT phase formation. The values of remanent polarisation P-r and dielectric constant epsilon(r) were found to decrease with the introduction of Nb. For example, in films heated at 700degreesC for 15 min, the P-r value of an unmodified PZT film was 31 muC cm(-2), compared to 17 muC cm(-2) for an x=0.05 PNZT film, whilst respective relative permittivity values fell from 1190 to 600. The highest Nb concentration film, x=0.07, did not display any switchable polarisation characteristics, which is consistent with high levels of intermediate pyrochlore phase.