PREFERENTIAL ORIENTATION AND DIELECTRIC PYROELECTRIC PROPERTIES OF SOL-GEL-DERIVED PB(MG,ZN)(1/3)NB2/3O3 THIN-FILMS

Thin films of Pb(Mg, Zn)(1/3)Nb2/3O3 (PMZN) were fabricated by spin casting the partially hydrolyzed Pb-Mg-Zn-Nb-O complex alkoxide sols on (111) Pt-coated MgO(100) planes. Analysis of the isothermal transformation data indicated that the growth of perovskite grains from the pyrochlore matrix is a diffusion-controlled process with an initial fast nucleation. The effect of water concentration in the sol on the preferential orientation of perovskite grains in the corresponding thin film was examined. A strong preferential orientation of (100) perovskite was obtained in the PMZN thin film derived from the sol having a molar ratio of H2O to total metal alkoxides (R(w)) of 2. A small-angle x-ray scattering (SAXS) experiment in the Pored region indicated that weakly branched precursor systems led to highly (100)-oriented perovskite grains after thin-him formation. The pyroelectric coefficient and the corresponding figure-of-merit were controlled by suitably varying the degree of preferential orientation during the fabrication of thin films.