Piezoelectric anisotropy

Figure 18.8 Piezoelectric anisotropy versus dielectric anisotropy for various oxygen octahedra ferroelectrics with 3m, mm2, and 4mm point group symmetries. From Ref. [42].

Budimir, M., Damjanovic, D., and Setter, N. (2003) Piezoelectric anisotropy-phase transition relations in perovskite single crystals./. Appl. Phys., 94 (10), 6753-6761. 

Damjanovic, D Budimir, M Davis, M and Setter, N. (2006) Piezoelectric anisotropy Enhanced piezoelectric response along nonpolar directions in perovskite crystals. /. Mater. Sci., 41 (1), 65-76. 

Figure 2. Effect of piezoelectric anisotropy on the single-crystal orientational behavior. Left inset embodies the polar response of the normalized piezoelectric behavior for different anisotropy factors. Note that the optimal orientation changes as the degree of anisotropy increases. Left inset shows the optimal orientation of each single-crystal, as a function of crystallographic anisotropy. Note that contrary to what it is intuitively expected, in the limit of high anisotropy, A 2/3, the crystallographic orientation at which highest piezoelectric strains will occur will asymptotically align with the direction of the applied field. Furthermore, the optimal orientation for materials with weak anisotropy will asymptotically converge to 0=54.16°.

Damjanovic Establishes a connection to continuum Gibbs free energy representation, which potentially accounts for piezoelectric anisotropy Not yet formalized as an atomistic description. Challenging to incorporate domain walls, defects. 6... 

An improved version of the 0-3 composite incorporated modified lead titanate because of its greater piezoelectric anisotropy [8]. The lead titanate filler is produced by water-quenching the ceramic to exploit the high strain in the material (approximately 7%) to produce fine powders. The average particle size was about 5 jum. To fabricate the composite bodies, the piezoelectric powders and chloroprene rubber were mixed... 

To predict the effective electromechanical properties of the 0-3 composite with the spheroidal inclusions, different averaging methods are applied [15, 16, 23-25]. Our current study is carried out within the framework of the model [15] that has first been applied to the 0-3 composite based on the (Pbi.jrCai)Ti03 FC with the large piezoelectric anisotropy. In this model the shape of each inclusion (Figure 1, component 1) is described by the equation... 

Figure 3. Volume-fraction dependence of normalized dielectric permittivity p a andb), normalized piezoelectric coefficients j8rf(c) and and factors of the piezoelectric anisotropy (e) and...

Figure 11). It can be accoimted for by the presence of FC with the large piezoelectric anisotropy and by comparable values of electromechanical constants of the SC and FC components in the composite. Values of the piezoelectric coefficients d and 33 (see... 

The results discussed in this chapter can promote the selection of the proper SC and FC components for novel composites with high piezoelectric sensitivity, large piezoelectric anisotropy, considerable hydrostatic response, and other remarkable effective parameters. It is believed that the development of high-performance composites will be attraetive for modem piezotechnical applications (sensors, hydrophones, transdueers, etc.). 

The magnitude of the piezoelectric response owing to applications of stress or strain transverse to the chain axis is much greater than the response owing to application of stress or strain parallel to the chain axis. This anisotropy in electrical response reflects the mechanical anisotropy of extended chain polymer... 

The anisotropy of piezoelectricity in oriented polymer films is quite different among polymers. The piezoelectric effect in oriented polypeptide films is greatest when elongated along a direction at 45° to the draw-axis. On the contrary, the effect is most remarkable for elongation along the draw-axis for roll-drawn poly(vinylidene fluoride) film. 

In the usual experiment where E0 = 0, the term kSE in Eq. (9) does not make any contribution as far as the electrical response with the same frequency as the mechanical excitation is concerned. However, as will be described in 2.2 and 2.4, the piezoelectric constant of a polymer film is sometimes a function of the electrostriction constant which plays an important role in the anisotropy and relaxational behavior of the piezoelectric effect. 

The piezoelectricity of roll-drawn PVDF exhibits a strong anisotropy which has been investigated by Nakamura and Wada (1971). The result is illustrated in Fig. 24. The e-constant is greatest when the film is stretched along the draw direction, in contrast to the anisotropy in Fig. 9. The... 

In Group (B), the piezoelectricity is strongly affected by the electro-striction effect in its anisotropy and relaxational behavior. 

With this background, we have proposed and developed a new purely electrical method for imaging the state of the polarizations in ferroelectric and piezoelectric material and their crystal anisotropy. It involves the measurement of point-to-point variations of the nonlinear dielectric constant of a specimen and is termed scanning nonlinear dielectric microscopy (sndm) [1-7]. This is the first successful purely electrical method for observing the ferroelectric polarization distribution without the influence of the screening effect from free charges. To date, the resolution of this microscope has been improved down to the subnanometer order. 

Ma S, Fuh JYH, Zhang YF, Lu L (2010) Synthesis of anisotropie lead titanate powders for templated grain growth of textured piezoelectric ceramics. Surf Rev Lett 17 159-164... 

The orientational dependence of 22 (the longitudinal strain along the y-axis) and 33 (the longitudinal strain along the z-axis) possess the same mathematical form, while the details of the properties are summarized on the anisotropy ratio. Ay, a function of the piezoelectric coefficients. 

Dunn, M L. 1995. Effects of grain shape anisotropy, porosity, and microcracks on the elastic and dielectric constants of polycrystalline piezoelectric ceramics. Journal of Applied Physics 78 [3] 1533-1541. 

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