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The effects of external stress cooperated with temperature, measuring frequency and measuring electric field on the fatigue properties of Bi 3.25 La 0.75 Ti 3 O 12 thin films are investigated. The fatigue properties can be improved by the external stress (both tensile and compressive). The larger the stress is, the more obvious the improvement is. Meanwhile, the stress-induced improvement is more distinct in the films annealed at a higher temperature. In addition, when measured at a higher frequency or at a larger electric field, the films show better fatigue properties, and the improvement caused by stress is more evident. The experimental results can be explained well by the mechanism in which the charged defects pin the domain walls during electric cycling.

Single phase ceramics CaCu3Ti4.0O12 and CaCu3Ti3.9O12 have been prepared using the traditional solid-state reaction method. Compared with the stoichiometric ceramics CaCu3Ti4.0O12, Ti-deficient ceramics CaCu3Ti3.9O12 have the larger lattice parameter, the higher force constant, and smaller dielectric constant and the lower dissipation factor, although their fundamental characters of dielectric response are similar. Their characteristic relaxation frequencies are not well fitted with the Arrhenius Law but a tentatively supposed relation. With the Cole–Cole Law, the fitted broadened factors of dissipation peaks are 0.5433 and 0.8651 for CaCu3Ti3.9O12 and CaCu3Ti4.0O12, respectively. All facts mentioned above imply that mutually correlated motion of Ti ions or defects may be expected to be responsible for the giant dielectric constant and high dissipation factor of CaCu3Ti4.0O12.

Bi4Ti3O12 (BiT), Bi3.25La0.75Ti3O12 (BLT), Bi4−x/3Ti3−xNbxO12 (BTN) and Bi3.25−x/3La0.75Ti3−xNbxO12 (BLTN) thin films have been prepared by pulsed laser deposition. BTN and BLTN films exhibit a maximum in the remanent polarization Pr at a Nb content x=0.018. At this Nb content, the BLTN film has a Pr value (25 μC/cm2) that is much higher than that of BiT and a coercive field (E c =120 kV / cm ) similar to that of BiT. The polarization of this BLTN film is fatigue-free up to 109 switching cycles. The high fatigue resistance is mainly due to the substitution of Bi3+ ions by La3+ ions at the A site and the enhanced Pr arises largely from the replacement of Ti4+ ions by Nb5+ ions at the B site. The mechanisms behind the effects of the substitution at the two sites are discussed.

An uneven distribution of stress in the thickness direction was introduced into Landau theory to investigate the behavior of phase transformations of ferroelectric thin films. Extensive stress induced a decrease of Curie temperature and polarization while an increase of susceptibility near the surface. Compressive stress induced an increase of Curie temperature and polarization and a decrease of susceptibility near the surface. There exist size-driven and stress-driven phase transformations only for the extensive stress cases.