Showing papers on "Ferroelectric ceramics published in 1972"
TL;DR: In this paper, the authors studied the changes in the hysteresis loops which occur with aging, a s shown in Fig. 1, and indicated that process (2) or (3) is its principal cause.
Abstract: N THE ferroelectric and piezoelectric applications of BaTiOa I and Pb(Zr,Ti)O,, dependence on time of many of their physical properties is encountered; this phenomenon is usually detrimental but is sometimes useful. Since aging is commonly considered to be related to the mobility of the ferroelectric domain structure, information on the nature of the aging process can be obtained by studying the changes in the hysteresis loops which occur with aging, a s shown in Fig. 1. A “fresh” ceramic sample of BaTiO, (just cooled to a temperature below the Curie point) exhibits a normal loop which on aging constricts gradually, resulting in decreasing remanent polarization. The rate and amount of constriction during aging are very sensitive to impurities and to slight variations in the Ba-Ti ratio. In the extreme case, the remanent polarization vanishes. This behavior can easily be confused with the double hysteresis loops exhibited by BaTiO, and PbZrO, as a result of fieldenforced paraelectric-ferroelectric and antiferroelectric-ferroelectric transitions, respectively. The constriction disappears if the sample is subjected to strong ac fields for prolonged times; this process is called deaging. The extremely constricted loop can be viewed as the result of reestablishment of the aged domain pattern after each half cycle. Strong fields are needed to disturb this pattern; however, after this disturbance a memory of the original state is retained, demonstrating that aging involves stabilization of the domain pattern. There is a general agreement’ that such stabilization occurs, but several mechanisms are possible: (1) Gradual equilibration of the domain pattern with respect to sizes and types of domains, with minimization of elastic and dielectric free energy.’*’ (2) Segregation of impurities and vacancies on domain walls and crystal boundaries. (3) Ordering of impurities and vacancies inside the ferroelectric domains with respect to the polar axis. Microscopy of single crystals and ceramics has demonstrated that process (1) occurs; however, its role in stabilization of the domain pattern is unclear. In the present work, an experiment was conducted that demonstrated aging simply and indicated clearly that process (2) or (3) is its principal cause. The ceramic samples were solid
102 citations
TL;DR: In this paper, a new type of image storage and display device is described in which the image is stored by means of a longitudinal electrooptic scattering effect in ferroelectric ceramics.
Abstract: A new type of image storage and display device is described in which the image is stored by means of a longitudinal electro‐optic scattering effect in ferroelectric ceramics. The stored image can be viewed directly or projected onto a viewing screen by using transmitted or reflected, polarized or unpolarized, white or monochromatic light. The device has the capability of selective erasure of part or all of the stored image.
94 citations
TL;DR: In this paper, the pyroelectric properties of hot-pressed lanthanum doped PZT X/65/35 ferroelectric ceramics have been evaluated to evaluate their potential as pyro-electric infrared detector materials.
Abstract: The pyroelectric properties of hot-pressed lanthanum doped PZT X/65/35 ferroelectric ceramics have been studied to evaluate their potential as pyroelectric infrared detector materials. The pyroelectric coefficients ranged from 3.5 × 10-8 to 17.0 × 10-8 (coul/cm2 °C) for lanthanum compositions from X = 0 to 8. The dielectric properties have also been measured over this compositional range. Thermal noise is shown to be dominant in detectors made from these materials for frequencies between 1 Hz and 1000 Hz. A detectivity at 100 Hz of 108 cm(Hz)4/W has been achieved in these materials.
47 citations
TL;DR: In this article, dielectric and optical fatigue effects in 8/65/35 lanthana modified lead zirconate-lead titanate (PLZT) ferroelectric ceramics have been observed in respense to 60 Hz sine wave switching.
Abstract: Dielectric and optical fatigue effects in 8/65/35 lanthana modified lead zirconate-lead titanate (PLZT) ferroelectric ceramics have been observed in respense to 60 Hz sine wave switching. Erratic behavior in Ee is attributable to microcracking near the surface electrodes. In addition, after N ∼ 105 cycles, the remanent polarization, PR, decreases as the logarithm of N. The birefringence parameter decreases linearly with PR over the entire range of 102 << N << 108 cycles.
38 citations
TL;DR: In this article, Lanthanum-doped lead zirconate-titanate ferroelectric ceramics (PLZT) were tested using the pulse-echo technique at 20 MHz and phase transitions occurring within the range 269° to 300°C were detected in poled and unpoled Pb1.02-xLax(Zr0.65Ti0.35)O3 with x=0.00 to 0.15.
Abstract: Lanthanum-doped lead zirconate-titanate ferroelectric ceramics (PLZT) were tested acoustically using the pulse-echo technique at 20 MHz. Phase transitions occurring within the range –269° to 300°C were detected in poled and unpoled Pb1.02-xLax(Zr0.65Ti0.35)O3 with x=0.00 to 0.15. For x=0.00 to 0.08 a phase transition observed between 0° and 100°C was defined by changes in the longitudinal sound velocity as great as 5% accompanied by pronounced absorption peaks. Measurements of resonance and electromechanical coupling in poled samples indicate that this transition involves 2 ferroelectric phases. The acoustic techniques reported made possible the detection of the subtler phase transitions in PLZT ceramics with a degree of sensitivity much higher than that available from the more conventional techniques. Both poled and unpoled samples may be tested by this technique, so that the influence of domain orientation on the transitions observed can be demonstrated.
25 citations
TL;DR: In this paper, a review of developments in Europe in the broad field of ferroelectrics including the use of such materials in the closely related fields of pyroelectric and non-linear optics is presented.
Abstract: The paper reviews developments in Europe in the broad field of ferroelectrics including the use of such materials in the closely related fields of pyroelectrics and non-linear optics. Infra-red detection and displays are discussed in connection with pyroelectric image tubes and non-linear optical up-conversion. Other applications described include optical digital light defectors for printing, displays and optical stores, and electro-optic and acousto-optic modulation for Q-switches in laser applications and as modulators in display tubes. Attempts to improve piezoelectric ceramic resonators include suppression of ageing with dopants, use of a novel mode of vibration and use of acoustic surface waves for i.f. circuits in T.V. receivers. Ceramics with a large positive temperature coefficient have been developed for a variety of applications. Transparent ferroelectric films are being widely investigated for display systems and materials closely related to ferroelectric ceramics are being developed for high p...
18 citations
TL;DR: In this article, the transverse linear electrooptic effect found in poled plates of ferroelectric ceramic PLZT 12/40/60 has been utilized in the construction of an optical modulator used for sensing low voltages.
Abstract: The transverse linear electrooptic effect found in poled plates of ferroelectric ceramic PLZT 12/40/60 has been utilized in the construction of an optical modulator used for sensing low voltages. The transparency of the La-modified lead zirconate titanate material, the large electrooptic coefficient rc = 1.4 × 10-10 m/V and index of refraction n = 2.55, and the low birefringence at zero field Δn0= -0.0011, make the ceramic convenient for the design of a small optical voltage sensor. This sensor, which is read out using fiber optics, can measure voltages in the range 0-50 V to ± 1 V with a response time of about 0.5 msec. The sensors can be designed to change transmittance by 0.9 %/V. This sensitivity increases considerably with increasing temperature because of concurrent increases in rc and decreases in Δn0. Both this thermal behavior and approximate calculations show rC and thus the large sensor sensitivity, to depend on an electrooptic effect intrinsic to the ceramic material rather than on domain real...
14 citations
TL;DR: In this paper, the pyroelectric properties of hot-pressed lanthanum doped PZT X165135 ferroelectric ceramics have been evaluated to evaluate their potential as pyro-electric infrared detector materials.
Abstract: The pyroelectric properties of hot-pressed lanthanum doped PZT X165135 ferroelectric ceramics have been studied to evaluate their potential as pyroelectric infrared detector materials. The pyroelectric coefficients ranged from 3.5 x lo-' to 17.0 x (coul/cmz "C) for lanthanum compositions from X = 0 to 8. The dielectric properties have also been measured over this compositional range. Thermal noise is shown to be dominant in detectors made from these materials for frequencies between 1 Hz and 1000 Hz. A detectivity at 100 Hz of IOm cm(Hz)i/W has been achieved in these materials.
10 citations
TL;DR: In this article, a strong quadratic nonlinear relation in certain ferroelectric ceramics between electric field and applied strain has been observed and the effect is strong enough for device application.
Abstract: We have observed a strong quadratic nonlinear relation in certain ferroelectric ceramics between electric field and applied strain. The effect is strong enough for device application and we have successfully fabricated several nonlinear surface acoustic wave devices using ferroelectric ceramics. Such devices provide electronically variable time delay. signal convolution, and pulse compression as well as a number of other signal processing functions.
9 citations
TL;DR: In this article, a strong quadratic nonlinear relation in certain ferroelectric ceramics between electric field and applied strain was observed and the effect is strong enough for device application.
Abstract: We have observed a strong quadratic nonlinear relation in certain ferroelectric ceramics between electric field and applied strain. The effect is strong enough for device application and we have successfully fabricated several nonlinear surface acoustic wave devices using ferroelectric ceramics. Such devices provide electronically variable time delay, signal convolution, and pulse compression as well as a number of other signal processing functions.
4 citations
TL;DR: The transverse linear electrooptic effect found in poled plates of ferroelectric ceramic PLZT 12/40'60 has been utilized in the construction of an optical modulator used for sensing low voltages.
Abstract: The transverse linear electrooptic effect found in poled plates of ferroelectric ceramic PLZT 12/40,'60 has been utilized in the construction of an optical modulator used for sensing low voltages. The transparency of the La-modified lead zirconate titanate material, the large electrooptic coefficient rc = 1.4 x m/V and index of refraction n = 2.55. and the low birefringence at zero field Ano = -0.0011, make the ceramic convenient for the design of a small optical voltage sensor. This sensor, which is read out using fiber optics, can measure voltages in the range 0-50V to k 1 V with a response time of about 0.5 msec. The sensors can be designed to change transmittance by 0.9%,T. This sensitivity increases considerably with increasing temperature because of concurrent increases in rc and decreases in An,,. Both this thermal behavior and approximate calculations show ro and thus the large sensor sensitivity. to depend on an electrooptic effect intrinsic to the ceramic material rather than on domain realignment.
TL;DR: In this article, a review of developments in Europe in the broad field of ferroelectrics including the use of such materials in the closely related fields of pyroelectric and non-linear optics is presented.
Abstract: The paper reviews developments in Europe in the broad field of ferroelectrics including the use of such materials in the closely related fields of pyroelectrics and non-linear optics. Infra-red detection and displays are discussed in connection with pyroelectric image tubes and non-linear optical up-conversion. Other applications described include optical digital light defectors for printing, displays and optical stores, and electro-optic and acousto-optic modulation for Q-switches in laser applications and as modulators in display tubes. Attempts to improve piezoelectric ceramic resonators include suppression of ageing with dopants, use of a novel mode of vibration and use of acoustic surface waves for i.f. circuits in T.V. receivers. Ceramics with a large positive temperature coefficient have been developed for a variety of applications. Transparent ferroelectric films are being widely investigated for display systems and materials closely related to ferroelectric ceramics are being developed for high p...
01 Jan 1972
TL;DR: In this paper, a review of developments in Europe in the broad field of ferroelectrics including the use of such materials in the closely related fields of pyroelectric and non-linear optics is presented.
Abstract: The paper reviews developments in Europe in the broad field of ferroelectrics including the use of such materials in the closely related fields of pyroelectrics and non-linear optics. Infra-red detection and displays are discussed in connection with pyroelectric image tubes and non-linear optical up-conversion. Other applications described include optical digital light defectors for printing, displays and optical stores, and electro-optic and acousto-optic modulation for Q-switches in laser applications and as modulators in display tubes. Attempts to improve piezoelectric ceramic resonators include suppression of ageing with dopants, use of a novel mode of vibration and use of acoustic surface waves for i.f. circuits in T.V. receivers. Ceramics with a large positive temperature coefficient have been developed for a variety of applications. Transparent ferroelectric films are being widely investigated for display systems and materials closely related to ferroelectric ceramics are being developed for high permittivity temperature-stable microwave substrates and resonators.