Effect of biphase on dielectric properties of Bi-doped lead strontium titanate thin films

Pb0.4Sr0.6TiO3 (PST) thin films doped with various concentration of Bi were prepared by a sol-gel method. The phase status, surface morphology and dielectric properties of these thin films were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance analyzer, respectively. Results showed that the thin films with the maximum dielectric constant and minimum dielectric loss were obtained for x=0.15. For x < 0.15, only pure PST perovskite phase were in the thin films. For 0.2 < x < 0.4, the PST/Bi2Ti2O7 biphase were obtained. The thin films with pure Bi2Ti2O7 pyrochlore phase were obtained for x=0.67. The biphase thin films had high tunability and high figure of merit (FOM). The FOM of PST/Bi2Ti2O7 biphase thin film was about 6 times higher than that thin films formed with pure perovskite phase or pure pyrochlore phase. (C) 2010 Elsevier Inc. All rights reserved.