Effect In Ferroelectric Crystals Research Articles

Effect of the compressive stress on both polarization rotation and phase transitions in PMN-30%PT single crystal

In this paper, we have investigated the dependence of both the electromechanical effect and the electrostriction on the compressive stress in PMN-30%PT single crystal on the basis of single domain polarization rotation model. In the model, the electroelastic energy induced by the compressive stress is taken into account. The results have demonstrated that the compressive stress can lead to a significant change in the initial polarization state in the crystal. The reason lies in the stress induced anisotropy which is the coupling between the compressive stress and the electrostrictive coefficients. Thus, the initial polarization state in single crystal is determined by the combination of both electrocrystalline anisotropy and the stress induced anisotropy. The compressive stress along the [100] axis can make the polarization in the crystal be perpendicular to the stress direction, and make it difficult to be polarized to the saturation. This model is useful for better understanding both the polarization rotation and electromechanical effect in ferroelectric crystals with the compressive stress present.

Polarization rotation theory for field-induced-phase transitions in BaTiO3 single crystal

We have proposed the polarization rotation theory to understand the underlying physics of the large piezoelectric effect in ferroelectric crystals by referring to the coherent rotation model in ferromagnetism. When both the electric field energy and crystalline anisotropy energy are taken into account, the polarization in BaTiO3 crystal can be rotated toward the field direction. The numerical results are in agreement with the experimental observations and have indicated the highly anisotropic polarization rotations and the field-induced-phases with different symmetries in the crystal. This theory is helpful for understanding the polarization reversal and the electromechanical effect in ferroelectric materials.

Ferroelectric-Specific Stark Effect in StoichiometricLiNbO3∶Feat Room Temperature

By means of EPR spectroscopy of LiNbO(3):Fe at room temperature (RT) it is shown that the Stark effect in ferroelectric crystals can be different from that observed in other materials. Novel properties appear when an external E field reverses the direction of the spontaneous polarization, the direction of the linear Stark shift stays the same with a reversal of the E field. The corresponding spectral line shifts can occur over a long time scale (hours). These properties seem to be a general feature of the Stark effect in ferroelectric crystals when the external E field exceeds the coercive field.

Phase-shifting point-diffraction interferometer developed by using the electro-optic effect in ferroelectric crystals

A novel and simple phase-shifting point-diffraction interferometer using a z-cut lithium niobate wafer is proposed. The pinhole is realized by an optical lithography process, aluminum deposition, and subsequent lift-off on the surface of the wafer. The phase shifting is obtained by inducing the electro-optic effect along the z crystal axis. We demonstrate experimentally the possibility of retrieving an aberrated wavefront.

On the interpretation of X-ray diffraction effects in ferroelectric crystals subjected to laser irradiation

In an earlier X-ray investigation of ferroelectric single crystals of LiNbO3:Fe and triglycine sulfate (3C2H5NO2. H2SO4) subjected to laser irradiation [Zhukov, Fetisov & Aslanov (1991). J. Appl. Cryst. 24, 74–76], a large increase (greater than 20%) in the integrated intensities of Bragg reflections was found. An attempt to explain the observed effects is given here with the aid of additional experimental results and consideration of the abnormal photovoltaic effect (APE) followed by a deformation of the domain structure of the crystal.

Experimental and theoretical investigations of the pyroelectric effect in ferroelectric crystals at low temperatures

Abstract The temperature dependence of the low-temperature pyroelectric response, Uπ, has been investigated by a dynamic method for a number of ferroelectric single crystals. The main features of the behaviour of Uπ, (T) are explained in the framework of the proposed microscopic model. Good agreement between theoretical results and experimental data for the uniaxial displacive-type ferroelectric Sn2P2S6 is obtained. In addition, some possible applications, based on the effect of the pyroelectric coefficient sign change, are proposed.

Models for the bulk photovoltaic effect in ferroelectric crystals

Three models for the bulk photovoltaic effect in electrooptic crystals are discussed. All models produce the same results. First, the photocurrent responsible for hologram storage is spatially shifted relative to the optical pattern that produced it. Second, the efficiency of hologram recording decreases with increases in the spatial frequency of the optical interference pattern. Third, the efficiency of hologram recording decreases for crystals exhibiting a strong bulk photovoltaic effect. The effect of finite electron transport length on volume-phase hologram storage is analyzed. It is shown that the resulting holograms are spatially shifted relative to the optical-intensity pattern that produced it. This phase shift affects beam coupling during hologram reading; it can be an aid in studying the bulk photovoltaic effect and the relative importance of the various mechanisms of hologram writing. The analysis also points out that the finite electron transport length reduces the ability of the crystal to store holograms if the spatial frequency of the optical interference pattern is increased.

The spectral characteristics of the photorefractive effect in barium-strontium Niobate crystals

The photorefractive effect in ferroelectric crystals is well known to be due to the formation of a local internal field which gives rise to the refractive index change via linear electrooptic effect.1,2 In LiNbO3 the most important role in formation of the internal field has been shown to be played by the bulk photovoltaic effect.3,4 However such mechanism appears is not the only one possible. In other cases the internal field is supposed to originate in screening.1,5

Electrooptical and photoelastic phenomena in ferroelectric crystals (survey)

Relations between optical and ferroelectric properties are discussed as a basis for analyzing and generalizing this author's and other authors' research data pertaining to the electrooptical, the photoelastic, and other effects in ferroelectric crystals.