Piezoelectric single crystals

In contrast to piezoelectric single crystals, such as quartz, the piezoelectricity of PZT ceramics decays with time due to relaxation. Experimentally it is found that on a large time scale (for example, months and years), the aging process can be accurately described by a logarithmic law. For example, the coupling constant k varies with time f as... 

Park, S.-E. and Shrout, T.R. (1997) Characteristics of relaxor-based piezoelectric single crystals for ultrasonic transducers, IEEE Trans. Ultrasound, Ferroelectrics and Frequency Control, 44, 1140-7. 

Lee, H. Y., Solid-state single crystal growth (SSCG) method a cost-effective way of growing piezoelectric single crystals, in Piezoelectric Single Crystals and Their Application, S. Trolier-Mckinstry, L. E. Cross and Y. Yamashita (eds), 160-77, 2004. 

Ferroelectrics are the prime material for piezoelectric applications in ceramic form, due to the discovery of the electrical poling process that aligns the internal polarization of the crystallites within the ceramic, and causes the ceramic to act in similar fashion to a piezoelectric single crystal. Three categories of applications have... 

Piezoelectric single crystals such as 128°Y-X (128°-rotated-Y-cut and X-propagation)— LiNbOj and X-112°Y (X-cut and 112°-rotated-Y-propagation)— LiTaOj have been extensively employed as SAW substrates for applications in VIF filters. A c-axis oriented ZnO thin film deposited on a fused quartz, glass or sapphire substrate has also been commercialized for SAW devices. Table 4.1.2 summarizes some important material parameters for these SAW materials. 

Sorokin BP, Turchin PP, Burkov SI, Glushkov DA, Alexandrov KS (1996) Influence of static electric field, mechanical pressure and temperature on the propagation of acoustic waves in LasGasSiOn piezoelectric single crystals. Proceedings of IEEE international frequency control symposium, pp 161-169... 

Fig. 13.4 Usage temperature range of various piezoelectric single crystals, showing different sensitivities (piezoelectric coefficient) (Reprinted with permission from Zhang et al. (2011). Copyright 2011 Elsevier)...

Electro-Optic Constants of Piezoelectric Single Crystals of CGG-Type... 

Piezoelectric Single crystal Quartz Freq. [Pg.99]

Fig. 9.1. Piezoelectric effect. (A) A quartz plate, cut from a single crystal. (B) By stressing the quartz plate, an electrical charge is generated. (After Curie, 1889.)...

Various crystalline materials with desired properties have been synthesized, and this has driven the utilization of single crystals in the production of semiconductor, opto-electronic, piezoelectric, and pyroelectric materials. 

The piezoelectric coefficients are third rank tensors, hence the piezoelectric response is anisotropic. A two subscript matrix notation is also widely used. The number of non-zero coefficients is governed by crystal symmetry, as described by Nye [2], In most single crystals, the piezoelectric coefficients are defined in terms of the crystallographic axes in polycrystalline ceramics, by convention the poling axis is referred to as the 3 axis. 

In many ferroelectric materials, the net piezoelectric effect is a result of both intrinsic and extrinsic responses. Here, intrinsic refers to the response that would result from an appropriately oriented single crystal (or ensemble thereof, in a polycrystalline sample). The extrinsic response is typically the result of motion of non-180° domain walls. The principle of these... 

Figure 2.4 Strain-field curves for < 001 > oriented 0.91PbZn1/3Nb2/303-0.09PbTi03 single crystals. The sample in (a) was poled at room temperature, where the resulting domain state is unstable (due to induction of tetragonal material associated with the curved morphotropic phase boundary), yielding substantial hysteresis. In (b) the crystal was poled at low temperatures to keep it in the rhombohedral phase. When measured at room temperature, the piezoelectric response is much more linear and non-hysteretic, due to the improved stability of the ferroelectric domain state. Data courtesy of S. E. Park.

In such a measurement, the sample is clamped as lightly as possible, and the displacement of the surface in monitored. The amount of sample clamping is important, because the mechanical constraints can impact the ferroelastic response of the sample. That is, in samples where the mechanical coercive stress is low, it is possible to change the domain state of the material by improperly clamping it in the sample fixture. This is especially important in elastically soft piezoelectrics, such as many of the relaxor ferroelectric PbTiC>3 single crystals. 

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