Structure and properties of (1-x)PZN-xPT thin films with perovskite phase promoted by polyethylene glycol

Perovskite ferroelectric (1-x)Pb(Zn1/3Nb2/3)O-3-xPbTiO(3) ((1- x)PZN-xPT) thin films were prepared on LaAlO3 (LAO) substrates with a polyethylene glycol (PEG)-modified sol-gel method. It was found that the introduction of the PEG in the precursor solutions dramatically promoted the formation of the perovskite phase while suppressing the pyrochlore phase. With the aid of PEG, (001)-oriented epitaxial perovskite (1-x) PZN-xPT thin films with x as low as 0.3 were successfully achieved without detectable pyrochlore phase. The perovskite phase was still dominant when x was reduced to 0.1 in which the composition is around the morphotropic phase boundary (MPB). The electric properties of our 0.7PZN-0.3PT films deposited on conductive LaNiO3-coated LAO substrates were characterized, and the films exhibited good dielectric, ferroelectric, and piezoelectric properties. An understanding on the mechanism of PEG promoting the perovskite phase and suppressing the pyrochlore phase has been developed through systematic investigation in this paper.