Об аномальном влиянии внешнего электрического поля на фазовый переход второго рода в тонкой сегнетоэлектрической пленке

In the framework of the phenomenological theory of Landau-Ginzburg-Devonshire, the features of the phase transition in a thin ferroelectric film in external electric field are investigated depending on the film thickness and the type of polarization fixed on its surface. It was found that the phase transition mechanism changes in an electric field. In addition to specific diffusing, which differs from diffusing in a bulk material by the appearance of a temperature range with an anomalously high susceptibility near temperature Tc, the phase transition shifts in temperature, and the shift value depends on the film thickness, its surface properties and in a weak fields does not depend on the field strength.

Ferroelectric Instability and Dimensionality in Bi-Layered Perovskites and Thin Films

The dielectric and thermal properties of Bi (bismuth)-layered perovskite SrBi2Ta2O9(SBT) are discussed in comparison with ferroelectric thin BaTiO3films. Although these two perovskites exhibit quite a different nature, the dielectric properties of BaTiO3thin film are similar to those in bulk SBT. The dielectric properties and pseudo-two-dimensional structure between SBT and thin film suggest that the bulk layered ferroelectric SBT is a good model of ultra-thin ferroelectric film with two perovskite layers, free from any misfit lattice strain with substrate and surface charge at the interface with electrodes. Based on the mechanism of ferroelectric phase transition of SBT, it seems plausible that the ferroelectric interaction is still prominent but shows a crossover from ferroelectric to antiferroelectric interaction in perovskite ultra-thin films along the tetragonal axis.

A Picowatt Energy Harvester

ABSTRACTThe authors describe an energy harvester circuit fabricated with integrated thin ferroelectric film capacitors on a silicon substrate. The harvesting mechanism is a folded double-beam cantilever with proof masses at both end points. Interdigitated electrode capacitors are located at the three points on the folded cantilever that are expected to experience maximum bending moment and should produce up to 5V as a function of external vibration. The die has the dimensions of 1.6mm on a side and is designed to be mounted in a TO-18 package transistor-style package. Due to its small size, the self-contained piezoelectric MEMs device should produce 50 picowatts in a 1g vibration environment while occupying little space.