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In this first paper an investigation of the pyroelectric effect is performed on iron-doped barium titanate (and also on cobalt-doped barium titanate) in the [1, 0, 0] direction, and during both continuous and limited irradiation.The results obtained reveal an alteration of both the ferroelectric and paraelectric properties, characterized especially by a polydomainization (appearance of a diffuse phase transition (T Tc).The results indicate that a new coupling between anharmonic properties and electrons must be introduced, during and after a photoelectric active irradiation. This point will be developed in the following paper.

Rhombohedral-phase PLZT ceramics can be made with a degree of transparency useful for electrooptic device applications. In addition to this transparency, there are several other significant characteristics: (1) intrinsic memory associated with the ferroelectric state, (2) changeable birefringence dependent upon remanent polarization, and (3) the capability of having remanent polarization switched at room temperature by moderate fields (∼ 10 kV/cm).This paper reports on the switching behavior of rhombohedral-phase PLZT ceramics under a variety of conditions that involve various combinations of electric fields, strain fields, and mechanical clamping. The experiments described in this paper demonstrate that under ordinary conditions, polarization reversal involves both 180° and less-than-180° domain switching and that the birefringence changes useful for electrooptic device applications depend critically on the extent to which less-than-180° domain switching takes place. Included in this paper are results on...

An array of electrically addressed light valves, referred to as a page composer or a pattern generator, is an important component of an optical memory. Ferroelectric and related materials, such as nematic liquid crystals, are attractive candidates for this application. This paper details the geometrical and optical characteristics and the various techniques for addressing a page composer for a holographic optical memory. Experimental data obtained on a nematic liquid crystal and single crystal bismuth titanate are presented. This data is compared with that previously reported for ceramic lead zirconate titanate and single crystal gadolinium molybdate. The major conclusions are that the optimum array is one in which the valves are individually addressed light scatterers. This operating mode is most conveniently achieved with a liquid crystal on an integrated semiconductor chip. The semiconductor circuits can also serve as the photodetector array for the optical memory. However, slow switching limits the us...

This is part I of a series of papers in which a qualitative model for a semiconducting uniaxial ferroelectric is developed in terms of Fe1-xS which was recently shown to be such a ferroelectric.Two types of charged defects are responsible for the anomalous behaviour, since they both weaken the polar coupling: (i) electronic defects belonging to the lattice (e defects) and (ii) vacancy-connected defects (v defects). The transition from the polar 2c phase to the paraelectric lc phase proceeds via a sequence of transitions which can be typified in the following scheme[image omitted] A TPS (Two Phase Structure) is a series of double junction rectifiers of alternate polarity that spontaneously form: the positive (negative) defects segregate into positive (negative) space-charge layers which having increased defect density are paraelectric. The space charge cancels the depolarizing field connected with the terminal charges of the polar layers which having decreased defect density are polar.It is shown that the ...

Continuing studies on the improvement of the optical quality of lanthanum modified lead zirconate titanate (PLZT) ceramics have shown that (1) bulk residual porosity and (2) chemical inhomogeneity are primary factors contributing to optical losses in thick plates of the material. This paper describes methods by which both of these major faults in the ceramic can be virtually eliminated. In addition, the optical and electrooptic properties of the improved material are presented and compared with those of previously available materials. Successful methods of eliminating residual porosity and enhancing chemical homogeneity resulted from studies which led to improved hot-pressing techniques and chemical preparation of the PLZT powders. Essentially all of the residual porosity was eliminated by introducing an oxygen atmosphere during the hot-pressing process. Chemical homogeneity was improved significantly by using high purity liquid solutions for preparing the PLZT powders. A combination of lead oxide and solutions of lanthanum acetate, zirconium alkoxide and titanium alkoxide was found to yield consistently good results. Optical tranhmission measurements were made on one-millimeter thick polished plates of representative PLZT composit~ons. Three sets of plates were prepared from (1) mixed oxides conventionally hot-pressed, (2) mixed oxides hot-pressed in an oxygen environment, and (3) chemically co-precipitated powders hot-pressed in an oxygen environment. For each composition measured, the optical transmission increased progressively for materials (1). (2). and (3). Moreover. materials (2) and (3) were progressively more homogeneous than (1) when viewed between crobsed polarizers. Electrooptic measurements for materials prepared by the three techniques discussed above showed no significant differences in electrooptic properties.

One of the important methods for the investigation of semiconductors is the measurement of the thermoelectric force. The determination of the type of conductivity by the Zeebeck-effect is useful for materials with small carrier mobilities, such as ferroelectric-semiconductors. For these types of materials the measurement of the Hall-effect is very difficult. Until recently there were only several papers with results of thermoelectric and electrothermic measurements in ferroelectric-semiconductors. These measurements permit the conductivity and mobility of carriers and the Fermi-level to be determined.