Structure and properties of (1-x)(0.6Pb(Zn1/3Nb2/3)O3-0.4Pb (Mg1/3Nb2/3)O3)-xPbTiO3 thin films with perovskite phase promoted by polyethylene glycol

摘要

The preferential formation of a pyrochlore structure is a knotty problem in the preparation of Pb(Zn1/3Nb2/3)O3 (PZN)-based thin film materials and its presence is significantly detrimental to the dielectric and piezoelectric properties. In this study, 40 mol% of PZN was replaced with Pb(Mg1/3Nb2/3)O3 (PMN) for obtaining a per ovskite composition around a morphotropic phase boundary (MPB), (l-x)(0.6PZN-0.4PMN)-xPT ((l-x)PZMN-xPT, PT: PbTiO3) where x = 0.23. The thin films with this compo sition were prepared with a polyethylene glycol (PEG) modi fied sol-gel method on LaAlO3 substrates. The microstruc tural evolution of the films on heat treatment was examined with X-ray diffraction. With the aid of PEG, the formation of the pyrochlore phase was suppressed and the perovskite phase formed directly from the amorphous gel film. The mul tilayer films with a thickness around 0.25 mu m showed a sin gle perovskite phase without any detectable pyrochlore struc ture. Microscopic images showed uniform grain size of a few tens of nanometers. The role of the polymer dramatically pro moting the perovskite phase was investigated with the aid of X-ray photoelectron spectroscopy and thermal analysis. The dielectric constant of the obtained film was 4160 at 1 kHz. The film demonstrated typical ferroelectric hysteresis loops and exhibited excellent piezoelectric performance.