Effect of Gd doping on dielectric properties and polarization behavior of lead zirconate titanate thin films

Highly (100)-oriented Pb(Zr_0.52Ti_0.48)O₃ thin films with different Gd dopants (PGZTx, x=0, 1mol%, 2mol%, 3mol%, 5mol% Gd) were prepared on Pt/Ti/SiO₂/Si substrates by the sol-gel technique and rapid thermal annealing (RTA) process. The dielectric properties of the PZT thin films with 1mol% Gd dopant is improved with increased dielectric permittivity and decreased dielectric dissipation. However, when Gd dopants are more than 2mol%, dielectric properties of the doped PZT thin films are deteriorated obviously including decrease of dielectric permittivity, increase of dielectric dissipation. At the saturation field, the irreversible polarization first increases when Gd content is 1mol% and then decreases when Gd contents are more than 2mol%, the reversible polarization remains almost constant in all PGZT thin films. The so-called Rayleigh law used to describe the hysteresis of ferromagnetic materials in the subcoercive regime can be extended to describe the subcoercive hysteresis in ferroelectric PGZT materials. The mechanism of the Gd dopant effect on the dielectric properties and polarization behavior is also discussed.