Ferroelectric and piezoelectric properties of Nb doped PZT films

Pb(Zr,Ti)O-3 (PZT) and Pb(Zr,Ti,Nb)O-3 (PNZT) thin films were grown on platinized silicon substrates by r.f. magnetron sputtering followed by a post-annealing treatment. The Niobium, Nb, concentration varied from 1 to 7 at.% by increment of 1 at.%. The effects of the Nb introduction on the PZT electrical properties, i.e, dielectric, ferroelectric and piezoelectric ones were investigated. The relative dielectric constant (epsilon (T)) was very sensitive to the Nb introduction; epsilon (T) reaches 1100 for a PNZT film doped at 2 at.% in comparison to 820 for a PZT film. The ferroelectric properties were also dependent of the doping level; in particular the remnant polarization reaches its maximum value for a 2 at.% Nb doped PZT film. The introduction of Nb enhances the piezoelectric properties of the films. The maximum value of d(33) varied from 55 pm/V for PZT films to 115 pm/V for a 2 at.% Nb doped films. For this doping level, e(31rem). reaches its maximum value: - 4.6 C/m(2). PNZT thin films, with weak Nb concentration (comprised between 1 to 2 at.%) are suitable for microsystems realization.