Showing papers on "Ferroelectric ceramics published in 1979"
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TL;DR: In this paper, pressure-induced ferroelectric to antiferroelectric (FE) phase transitions at ∼ 0.2 GPa of hydrostatic pressure were studied as a function of both hydrostatic and uniaxial stress, and two effects were observed: rotation of FE domains and the FE-AFE phase transition.
Abstract: Mechanical properties of ferroelectric ceramics with compositions Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3 and Pb0.97La0.02(Zr0.92Ti0.08)O3 have been studied as functions of both hydrostatic pressure and uniaxial stress. Measurements of ultrasonic velocity and sample strains have been made in order to characterize unpoled samples. Both materials have pressure‐induced ferroelectric (FE) to antiferroelectric (AFE) phase transitions at ∼0.2 GPa of hydrostatic pressure. Under uniaxial‐stress conditions two effects are observed: rotation of FE domains and the FE–AFE phase transition. These effects are separately resolved by the measurements, even though they occur in overlapping stress regions. The domain reorientation responses of the two materials appear to be nearly identical, but the FE–AFE transition begins at lower stress levels for the Nb‐doped material. This is presumably due to that material transforming into the orthorhombic (PbZrO3) phase, whereas the La‐doped material transforms into the tetragonal AFE pha...
13 citations
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TL;DR: In this paper, a simple method for determining quantitatively the fraction of 90°domain rotation in the tetragonal ferroelectric phase by measuring the changes of the intensity of X-ray diffraction has been put forward.
Abstract: The domain structure of ferroelectric ceramics changes in the process of polarization and in the course of application. This kind of change has a direct influence on the macroscopic properties of the materials. A simple method for determining quantitatively the fraction of 90°domain-rotation in the tetragonal ferroelectric phase by measuring the changes of the intensity of X-ray diffraction has been put forward in this article. The percentage of 90° domain-rotation in the process of polarization could be obtained directly as soon as the intensity ratios of I200 and I002 of the nonpolariza-tion and polarization are respectively measured out correctly. The structure factors and preferred orientation which may exist have been taken into account in the deduction of the formula. For PZT ceramics of 50/50(Zr/Ti), the fraction of 90° domain-rotation under different conditions of polarization has been calculated by using the above method. The result obtained are parallel to the changes of the macroscopic properties. A comparison with the indirect method was used previously in the mechanical strain experiments has been made. In addition, the problem of determining the internal stress prior to and after polarization by measuring the broadening of the diffracted X-ray lines has also been discussed.
7 citations
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01 Jan 1979TL;DR: The physical process involved is not the piezoelectric effect but rather the destruction of the remanent polarization by either a randomization of domains or by a polymorphic phase transformation to a nonferroelectric State as mentioned in this paper.
Abstract: Short duration electrical pulses with peak powers approaching a megawatt can be obtained by shock-wave compression of poled ferroelectric ceramics. The polarity of the electrical responses indicates that the physical process involved is not the piezoelectric effect but rather the destruction of the remanent polarization by either a randomization of domains or by a polymorphic phase transformation to a nonferroelectric State. Power supplies based on phase transformations are practical in that their electrical responses are relatively insensitive to the magnitude of the shock as long as the characteristic threshold conditions for the transformation are exceeded.
5 citations
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TL;DR: In this article, the authors considered the solution of the transient coupled problem corresponding to the responses of ferroelectric ceramics in the axial mode experiment for which the direction of wave propagation corresponds to the directions of remanent polarization.
2 citations
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TL;DR: In this paper, the (Ba, Sb)TiOO3 ferroelectric films of thickness 8-10 microm were obtained by the sintering method and the introduction of an admixture not exceeding 0.2 mol.% of Sb2O3 to BaTiO3 markedly influences the semiconductor properties of the ferroelectric film.
2 citations
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01 Jan 1979TL;DR: In this paper, a single-shot, shock-activated power supply was proposed, where electrical energy is stored in a ferroelectric element by the initial poling process, and the passage of a shock wave through the material releases part or all of this stored energy into an external electrical load by actually destroying (non-reversibly) the State of initial polarization.
Abstract: Electromechanical transducers made of ferroelectric ceramic materials such as those based on barium titanate (BT) or on various lead zirconate titanate (PZT) compositions have become widely used for a variety of applications over the past 25 years [1]. Most of these applications utilize the linear piezoelectric effect for the conversion between electrical and mechanical energy, and one of the prime advantages of the BT or PZT materials is that their piezoelectric coupling coefficients are large. Another kind of application of ferroelectric ceramics — one that is perhaps not as generally familiar — is based on non-linear and non-reversible processes that can take place in these materials. One example of this kind of application is the single-shot, shock-activated power supply [2,3]. In this device, electrical energy is stored in a ferroelectric element by the initial poling process, and the passage of a shock wave through the material releases part or all of this stored energy (into an external electrical load) by actually destroying (non-reversibly) the State of initial polarization. There are two important mechanisms by which the destruction of polarization may occur. The first is by domain reorientation processes [4] whereby the directions of the polarization vectors in the individual ferroelectric domains change from one preferred crystallographic axis to another in response to the external stress. This process tends to randomize the domains and dramatically reduce the net polarization of the ceramic. The second possible mechanism for shock-induced depoling is a structural phase transition [3,5] induced by the stress behind the shock front, which transforms the material into a non-ferroelectric State. When such a transformation occurs, the polarizations of the individual crystallites of the ceramic become zero, so that all of the initial poling energy is released.