Dielectric relaxation of lanthanum doped zirconium oxide

Lanthanum doped zirconium oxide (La-x-Zr1-xO2-delta) films, with La contents, up to x=0.35, were studied. Films were annealed at 900 degrees C to crystallize them into phases with higher kappa-values. Increasing the La content suppressed the monoclinic phase and stabilized the tetragonal or cubic phase. The highest dielectric constant was obtained for a lightly doped film with a La content of x=0.09, for which a kappa-value of 40 was obtained. This was accompanied by a significant dielectric relaxation, following a single Curie-von Schweidler power-law dependency with frequency, changing to a mixed Curie-von Schweidler and Kohlrausch-Williams-Watts relationships after annealing. The dielectric relaxation was most severe for lightly doped films, which had the highest kappa-values. The dielectric relaxation appears to be related to the size of crystal grains formed during annealing, which was dependent on the doping level.