Preliminary results on sol-gel processing of ⟨100⟩ oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 thin films using diol-based solutions

A novel sol-gel method is used here for the synthesis of air-stable and precipitate-free diol-based sols of 0.7Pb(Mg1/3Nb2/3)O-3-0.3PbTiO(3) (PMN-PT). Sols containing a 15 mol% lead excess have been used for the preparation of PMN-PT thin films. The films were deposited onto (111)Pt/TiO2/SiO2/(100)Si substrates, and crystallised in oxygen by Rapid Thermal Processing (RTP), using different temperatures and soaking times. Single perovskite films are obtained when treated at temperatures between 600 and 700 degrees C for 6 s. Those crystallised at other temperatures contain a secondary pyrochlore phase. This phase also appears in the films treated at 650 degrees C with soaking times longer than 6 s. PMN-PT films with a (100) preferred orientation were prepared by using a PbTiO3 seeding layer onto the substrate. These PMN-PT films present relaxor-type electrical properties. Dielectric permittivity, epsilon(T)(33), shows significant dispersion. Its temperature dependence presents a broad maximum at 110-130 degrees C, which position shifts towards higher temperatures with frequency. Ferroelectric hysteresis loops show high values of saturation polarisation but very low remanence. The piezoelectric activity of the films has been tested by the measurement of their local piezoelectric hysteresis loops.