Showing papers on "Lead zirconate titanate published in 1971"

Electrical Resistivity of Lead Zirconate Titanate Ceramics Containing Impurities

Abstract: Electrical resistivity and its temperature variation are measured for lead zirconate titanate ceramics containing various metal oxides as impurities. The impurities can be classified from their influence on the resistivity of ceramics into the following three groups. (1) Impurities which keep the resistivity nearly unchanged (e.g. Fe2O3). (2) Impurities which increase it enormously because of electron-hole compensation (e.g. Nb2O5). (3) Impurities which increase it at first (electron-hole compensation) and then decrease it (e.g. Cr2O3). The decrease of resistivity in group (3) seems to be caused by the generation of segregated impurity layers which enclose the grains in ceramics. This postulate is confirmed quantitatively by the measurements of resistivity of the ceramics in which impurities are injected by means of thermal diffusion.

Substitution of Bi and Nb Ions in Lead Zirconate‐Titanate

Abstract: Solid-state substitution of Bi and Nb ions in the perovskite crystal structure of Pb(Ti0.47Zr0.53)O3 was investigated by sample weight changes at 1150°C in an “equilibrium” PbO atmosphere. A model is discussed that includes the effect of charge neutralization, requiring weight losses for A-site substitutions and weight gains for B-site substitutions. Experiments support the substitution of Bi as Bi3+ on the Pb2+ A site and Nb as Nb5+ on the (Ti,Zr)4+ B site of lead zirconate-titanate. For each mole of BiO1.5 added to a specimen, 1.5 moles of PbO are lost; for each mole of NbO2.5 added, 0.5 moles of PbO are gained. These results agree with the proposed model and with ionic size arguments. The weight changes were time-dependent during the first 30 to 40 h at 1150°C. This behavior is accounted for by the presence of transient second phases.

Electrooptic Properties of Ba, Sn, and La Modified Lead Zirconate Titanate Ceramics

Abstract: Electrooptic effects observed so far in ferroelectric lead zirconate titanate ceramic materials are transverse electrooptic effects (linear, quadratic, and memory), strain-biased longitudinal electrooptic memory effect, and electrically controlled scattering. The electrooptic memory effects are related to variations of ceramic birefringence with remanent polarization. All the above electrooptic effects are found in Ba, Sn, and La modified lead zirconate titanate ceramics except electrically controlled scattering. Both the character and magnitude of these effects are strongly dependent on the composition and grain size of the ceramic material as well as on the temperature and light wavelength of observation. The results for the La modified ceramics, which can be made highly transparent, are discussed in the greatest detail. The various electrooptic effects are shown to arise either from orientation of ferroelectric domains or from field-enforced ferroelectric distortion of certain para-electric materials.

Measurement of Elasto-Optic Effect in Absorbing Materials by Ellipsometry*

Abstract: Strain-induced changes in the optical (dielectric) constants of silver films on lead zirconate titanate are determined ellipsometrically. In general, for a contaminant-free surface, the induced changes can be determined directly from the ellipsometer measurements. An additional advantage of the method is that it allows compensation for errors introduced by unavoidable mechanical vibrations. In the development of the theory, four-zone expressions are derived for the general case that includes the effect of extraneous signals caused by mechanical vibration.

Active compensators for ferroelectric-optical circuits

Abstract: Disturb pulse and fatigue effects have prevented or limited the use of ferroelectric materials as matrix addressed arrays of light valves suitable for optical memories, page composers, displays and printers. These problems can be optically balanced out by building an array of compensators out of a second piece of ferroelectric and applying to the compensator array the same disturb and polarization reversal history that the light valve array receives. Experimental data obtained on a lanthanum doped lead zirconate titanate ferroelectric ceramic shows the effectiveness of the active compensator technique in balancing out the disturb pulse effect. The optical balancing technique is not limited to ferroelectrics, but can also be applied to other optically active materials which do not have an absolute switching threshold and/or decay. The balancing technique can also be used to overcome the problems of elastic switching, which would normally cause light to escape momentarily from a half selected valve.

Ferroelectric ceramics for information storage and display

Abstract: 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.

The High Drive Properties of Whisker Reinforced Piezoelectric Ceramics

Abstract: The properties under high drive conditions of disk specimens of whisker reinforced composite ceramics are compared with the similar properties of commercially available nonreinforced ceramics of the same general family. The ceramics are of the lead zirconate titanate type with the whisker content of two grades of alpha alumina (sapphire) in five weight percent amount. Observations are made of stress, strain, electric field, resonant frequency, modulus, and electrical impedance. It is found that the whisker reinforced materials exhibit good linearity of stress, strain, resonant frequency, and modulus at high drive when compared with commercial samples of the same family, which are often markedly nonlinear. The conclusion is drawn that specimens, even of “soft” type ceramic, when whisker reinforced, are made “hard” in many of their properties. [This work was supported by the Office of Naval Research.]