Showing papers on "Ferroelectric ceramics published in 1977"
TL;DR: The piezoelectric constant of a uniaxially stretched and polarized poly(vinylidene fluoride) film decreases monotonically with increasing temperature in the range from 65 to 165°C.
Abstract: The piezoelectric constant of a uniaxially stretched and polarized poly(vinylidene fluoride) film decreases monotonically with increasing temperature in the range from 65 to 165 °C. After a specimen is cooled under open‐circuit conditions, the thermally stimulated current reverses in sign and exhibits a peak at around the glass‐transition temperature Tg. Reversible changes in infrared spectra before and after the poling process suggest that the dipoles in the β crystals of poly(vinylidene fluoride) can be aligned along the direction of an applied electric field. The alignment is strongly influenced by the amorphous region; the coercive field in P‐E hysteresis curve observed at 50 Hz increases rapidly at around Tg. Under a high electric field, the uniaxially stretched poly(vinylidene fluoride) film behaves above Tg in the same way as ferroelectric ceramics.
92 citations
TL;DR: In this article, a form is assumed for the equation giving the shock-induced polarization, which includes terms representing, respectively, a linear dielectric, a ferroelectric including the stress and field dependence of the remanent polarization, and a piezoelectric whose coefficients are proportional to the polarization.
Abstract: Electric fields existing in shock‐wave‐compressed specimens of poled ferroelectric ceramics are caused by both the piezoelectric effect and a randomization of the domains aligned in the poling process. The contribution of these effects to the electric field is governed by the dielectric equation of state of the material. In general, even the form of this equation of state is uncertain for the large electric field and stress values encountered in the shock‐compression process. In this work a form is assumed for the equation giving the shock‐induced polarization. It includes terms representing, respectively, a linear dielectric, a ferroelectric including the stress and field dependence of the remanent polarization, and a piezoelectric whose coefficients are proportional to the remanent polarization. An important prediction of this relation is that shock waves can increase the remanent polarization of a partially poled specimen. This effect has been observed, and the conditions under which it occurs are used to evaluate the equation of state of a representative material, PZT 65/35.
30 citations
TL;DR: In this article, a model was developed that takes into account the finite resistivity of ferroelectric ceramics compressed by shock waves propagating in a direction perpendicular to the remanent polarization vector.
Abstract: A model is developed that takes into account the finite resistivity of ferroelectric ceramics compressed by shock waves propagating in a direction perpendicular to the remanent polarization vector. This model is fit to data obtained from experiments on Pb0.98Nb0.02(Zr0.95Ti0.05)0.98O3 (referred to as PZT 95/5). The resistivity of this material in the stress range 1.6–3.2 GPa is about 7×104 Ω cm.
23 citations
7 citations
Patent•
19 Jan 1977
TL;DR: In this paper, a transparent ferroelectric ceramics was obtained by giving a body molded from powdered oxide a treatment to make its composition minute under the specifid condition and by giving it another treatment in order to make it transparent.
Abstract: PURPOSE:To obtain a transparent ferroelectric ceramics by giving a body molded from powdered oxide a treatment to make its composition minute under the specifid condition and by giving it another treatment to make it transparent.
2 citations
14 Oct 1977
TL;DR: In this article, the effects of one-dimensional compressive stress parallel to the polarized axis of ferroelectric ceramics Type I, II, and III (MIL-STD-1376) were tested.
Abstract: : The effects of one-dimensional compressive stress parallel to the polarized axis of ferroelectric ceramics Type I, II, and III (MIL-STD-1376) were tested. Material of each type was obtained from five manufacturers and tested to determine the dependence on stress of the constants g33, d33, and KT33 and dielectric loss tangent. Data and relative comparisons between material types were determined. (Author)