Preparation, Characterization and Domain Structures in Thin Films of the Ferroelectric, Lead Iron Niobate.

This thesis reports the preparation of lead iron niobate, Pb(Fe_{1/2}Nb _{1/2})O_3 (PFN), thin films by sol-gel processing, the physical and electrical characterization of the resultant thin films by XRD and TEM, measurements of their ferroelectric properties and the observations of the domain structures and phase transitions in the films with large perovskite grains. Pb(II) t-butoxide, Nb(V) ethoxide and Fe(II) acetate are used as precursors and PFN thin films consisting of pure perovskite phase are first successfully obtained on Pt-coated Si substrates. The phase evolution for the PFN thin films under different annealing conditions are investigated and the factors causing the formation of pyrochlore phase PFN are discussed. For sol-gel derived PFN thin films, the mechanism of forming the perovskite phase is found to occur in two ways: one is through a transformation from the pyrochlore phase and the other is nucleation in the gels directly and then growth during annealing. The optimum process for the fabrication of PFN thin films with large perovskite grains is developed. Ferroelectric domain configurations and their characteristic variation with the temperature in both PFN ceramics and thin films are observed "in-situ" by TEM for the first time using a cold-stage. The phase transition from the ferroelectric to paraelectric state is diffuse at the Curie temperature. Antiferromagnetic microdomains are first seen by TEM appearing within the ferroelectric macrodomains in the PFN thin films when the specimens are cooled down to the Neel temperature. The PFN thin film on Pt-coated Si(100) has a remnant polarization of 0.011muC/cm ^2 and a dielectric constant of ~460 at room temperature and 50 Hz. Both the temperature dependence of bf{P_ {s}} and varepsilon also show the relaxation behavior of PFN at bf{T_{c}}.