Processing and characterization of Pb(Zr, Ti)O₃films, up to 10 μm thick, produced from a diol sol-gel route

A recently developed diol sol-gel route has been modified in order to produce multilayer PbZr_0.53Ti_0.47O₃films on platinized sapphire substrates. Up to 20 depositions of a 1.1 M sol were carried out leading to a final film thickness of 10 μm. A similar thickness could be achieved from 12 coatings of a more concentrated 1.6 M sol. Decomposition and crystallization of the multilayer coatings were performed using a two-stage prefiring sequence, at 350 °C and 600 °C, followed by a final firing step at 700 °C. Ferroelectric remanant polarization increased with increasing film thickness to a value of 40 μC cm⁻²for a 10 μm film, with a corresponding coercive field of 30 kV cm⁻¹; the relative permittivity of this film was ∼1000 and the dissipation factor 0.04. The thickness dependence of relative permittivity could be modeled on a simple series capacitor circuit representing the ferroelectric Pb(Zr, Ti)O₃(PZT) film and low-permittivity interface layers; but other possible contributory factors are also discussed.