Electrooptic Ceramics Research Articles

Specific solid state features of transparent ferroelectric ceramics

Characteristic features of chemical composition, structure and properties of transparent ferroelectric ceramics (TFC) are revealed from the analysis of the known materials. From considerations of the microstructure of TFC, it is shown that practically no space charge accumulates on the grain boundaries. Essential physical and technological factors responsible for light transmittance are analyzed, and criteria that can be used for the search for new TFC compositions proposed. Some TFC properties are explained in terms of highly doped and compensated ferroelectrics. Specific features of TFC in comparison with electrooptic single crystals and opaque ferroelectric ceramics are discussed.

Induced absorption in electrooptical PLZT ceramics and SrTiO3 crystal with electron pulse irradiation

Pulsed electron irradiation of ferroelectric PLZT ceramics or single-crystal SrTiO3 induces a short-lived optical absorption ΔD(t). The dependences of the kinetics of transient absorption on temperature and/or photon energy has been investigated. The transient absorption in the region hν > 2.0 eV is probably due to the creation of oxygen vacancies under electron irradiation, while the absorption in the region hν < 2.4 eV is due to the redistribution of defects in the cation sublattice. Dependences ΔD(hν), ΔD(t), and ΔD(t) for SrTiO3 and PLZT are similar. It is suggested that the quantitative differences between them are caused by the relatively higher mobility of the defects in SrTiO3.

Fabrication of Transparent PZLT Ceramics by Atmosphere Sintering

Pressure-less fabrication process of lanthanum-modified lead zirconate titanate (PLZT) electrooptic ceramics has been developed. Fine-particle PLZT powders having excellent reaction and homogeneous composition were fabricated by a chemical preparation method using inexpensive starting materials. Optically transparent PLZT ceramics were obtained by sintering this chemically-prepared powder under O2-gas flow and atmosphere PLZT powder.

Microstructure and properties of some electrooptic ceramics

Abstract This paper deals with the hot-pressed tungsten-bronze typed electrooptic ceramics with the grain oriented behaviors, the mechanical properties of pore-free PLZT ceramics with the internal stress, the anisotropies induced by poling and the aging changes, and others.

New transparent ceramics for electro-optical applications

Abstract Transparent electro-optic ceramics have been prepared with compositions in the solid solution series Ba6–1.5xLaxNb8Ti2O30 (BLTN). They show relatively low permittivities and high extinction ratios in the transversal electro-optic effect. They could be able to replace PLZT in some high frequency applications.

Driving voltage calculation for a ferroelectric display device

The mixed boundary conditions problem for the potential in a ferroelectric display with opposite interdigital electrode arrays is solved by a Fourier series whose coefficients are determined non-finally. The results so obtained are applied to the device based on the quadratically field-induced birefringence exhibited by electrooptic ceramics such as PLZT 9/65/35.

Defect structure and properties of electro-optic PLZT ceramics

The single phase widths of electro-optic PLZT x/65/35 ceramics have been studied as a function of La concentration x. The PbO losses corresponding to the upper and lower limits of the single phase region are measured by the thermo-gravimetric method of controlling the atmosphere. Also, the density approach, corresponding to the single phase region, has been tried for almost completely pore-free specimens prepared by two-stage processing. The defect formulae are discussed so as to fit both the PbO loss data and the bulk density range.

Single Monitor Stereoradiological Television System Using PLZT Electrooptic Shutters

A new family of materials consisting of lead lanthanium zirconate titanate (PLZT) has evolved from recent advances in ferroelectric ceramics. PLZT electrooptic ceramics may be used as electronically triggered high-contrast optical shutters in lightweight stereoscopic viewing devices. A PLZT electrooptic shutter stereoradiology system in which dual x-ray tubes are used to generate stereo pairs of fluoroscopic images is presented. This system requires only a single television monitor for stereoscopic viewing by one or more observers. The viewer which contains the optical shutters is compact, light-weight, and can be attached easily to normal eyeglasses.

Electrooptical properties and photoinduced effects in plzt ceramics applications to optical storage and processing of information

After defining the properties of transparent lead-lanthanum zirconate-titanate ceramics (PLZT) we report the results of holographic and digital recording in quadratic electrooptic ceramics Pb0.91La0.09(Zr0.65Ti0.35)0.9775O3. Photoinduced refractive index changes in these ceramics by deflected and modulated argon laser beams, the behaviour of the diffraction efficiency versus light power density and applied field, the possibility of image selection and optical selective erasure are explained phenomenologically in terms of a photoinduced field model.

Observation of field-induced microstructure in β phase of 8/65/35 PLZT electro - optic ceramics

A chemical etching technique has been found which reveals a complex microstructure in the field-induced β phase of lanthanum zirconate-titanate electro-optic ceramics having a composition 8/65/35. This microstructure in the electrically depoled state is irregular, while that in the electrically poled state is highly lamellar in character. Similar patterns were induced by mechanical strain. No evidence of microstructures was found in the thermally depoled α phase.

Fabrication of Transparent Electrooptic PLZT Ceramics by Atmosphere Sintering

PLZT electrooptic ceramics were fabricated by a unique atmosphere sintering technique. The ceramics produced were significantly more transparent than those obtained by ordinary O2 sintering methods; in fact, they were comparable in transparency to those obtained by hot‐pressing. To achieve good transparency, the powder must be batched with excess PbO, which at the sintering temperature is present as a liquid phase at the grain boundaries. Sintering was conducted at 1200°C for 60 h in an atmosphere containing O2 and a relatively high partial pressure of lead oxide.

Electrooptic ceramics as wavelength selection devices in dye lasers

The output center wavelength of a rhodamine 6G dye laser was tuned by using variable birefringence filters in the cavity. The electrooptic properties of two different lead lanthanum zirconate titanate (PLZT) ceramics were used in these filters to achieve up to 120 Å of wavelength tuning. Spectral bandwidths varied from 20 to 120 Å with these particular filters.

A new longitudinal display mode for ceramic electrooptic devices

A new longitudinal mode of operation for the lanthanum-modified lead zirconate titanate (PLZT) ferroelectric electrooptic ceramics is described. Potential applications include displays and shutters.

Improved Hot‐Pressed Electrooptic Ceramics in the (Pb,La)(Zr,Ti)O3 System

Physical, electrical, and optical properties of selected compositions within the lead lanthanum zirconate‐titanate (PLZT) system are presented, including chemically and thermally etched microstructures, examples of residual porosity defects, temperature dependence of remanent polarization and coercive field, lateral switching strains, and thermal expansion and optical transmission data. Optical‐quality ceramics were produced by stringent raw material selection and improved ceramic processing and hot‐pressing. Optimum results were obtained from starting oxides with higher purity (99.9%) and smaller particle size (&lt;2 μm) than those used in previous investigations. These oxides were processed by methods developed to minimize segregation and promote chemical homogeneity and hot‐pressed at temperatures (1050° to 1250°C) higher than those used previously to remove residual porosity.

Ferroelectric ceramics for information storage and display

The electrooptic properties of hot-pressed lead zirconate titanate ceramics and their applications are reviewed. Coarse-grained, bismuth-doped ceramics with average grain size greater than 2 ώm have light scattering properties that can be varied by switching the orientation of the ferroelectric polarization. Fine-grained bismuth-or lanthanum-doped ceramics have an effective birefringence that can be varied either by applying an external electric field (conventional electrooptic effect) or by partially switching the remanent polarization (electrooptic memory effect). Ba, Sn, or La modifications of the lead zirconate titanate system produce materials with improved switching characteristics and electrooptic effects similar to those of fine-grained bismuth-or lanthanum-doped ceramics. Lanthanum modified lead zirconate titanate (PLZT) is significantly more transparent than other electrooptic ceramics. The PLZT system includes materials with electrooptic memory and either linear or quadratic electrooptic effects. The electrooptic properties of modified lead zirconate titanate ceramics, especially PLZT, combined with localized switching and modulation capabilities are particularly suitable for information storage and display devices.

Ferroelectric electrooptic ceramics with reduced scattering

Ferroelectric lead zirconate-titanate ceramics appear promising for use as electrically controlled retarders because both conventional electrooptic and nonvolatile incremental retardation changes can be induced in areas as small as 25 µ on a side. One particular composition, Pb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.97</inf> La <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.02</inf> Zr <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.65</inf> Ti <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.35</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> , has so far proved superior to all other rhombohedral lead zirconate-titanates when judged by either the conventional electrooptic retardation variation with applied bias voltage, or the nonvolatile incremental retardation change with remanent polarization state of the ceramic. Furthermore, this same lanthanum-doped composition exhibits a marked decrease in undesirable light scattering when compared with extensive data on the same composition with bismuth doping. Scattering also decreases with increasing wavelength λ, and the ceramic transmittance is greater than 85 percent for 3 µ<λ<8 µ with sample thickness less than 50 µ. This increased transmittance now makes feasible the construction of multistage ceramic electrooptic systems.