PZT compositions

In the converse piezoelectric effect one usually applies voltage V or electric field E on the sample and measures displacement AZ or strain A///. From relation Al = 0Z33 V for the longitudinal effect, we see that even for materials with exceptionally high piezoelectric coefficient (do3 = 2000pm/V in pzn-pt) the displacement Al is only around 2 nm if 1 V is applied on the sample. For the same voltage the displacement is reduced to 0.2 nm in a typical pzt composition and to only tn 2 pm in quartz. The displacement can be increased by application... 

The first piezoceramic to be developed commercially was BaTi03, the model ferroelectric discussed earlier (see Section 2.7.3). By the 1950s the solid solution system Pb(Ti,Zr)03 (PZT), which also has the perovskite structure, was found to be ferroelectric and PZT compositions are now the most widely exploited of all piezoelectric ceramics. The following outline description of their properties and fabrication introduces important ideas for the following discussion of the tailoring of piezoceramics, including PZT, for specific applications. It is assumed that the reader has studied Sections 2.3 and 2.7.3. 

Fig. 6.8 Coupling coefficient kp and permittivity er values across the PZT compositional range. (After Jaffe et al. [1].)...

The substitution of lead by barium enhances the piezoelectric properties which peak when Pb/Ba I. At this and higher barium contents the structure changes to tetragonal with the polar axis parallel to the A-site tunnels. There is a morphotropic boundary, similar to that found in PZT compositions, and peak values of piezoelectric properties are found near the Pb1/2Ba1/2Nb206 composition. d33 rises to 220 pCN-1 and d31 rises to — 90pCN 1, while Qm increases to 300 and the Curie point falls to 250 °C thus most of the features peculiar to... 

In practice, with most PZT compositions, Eq. (6.78) may underestimate the energy released because domain reorientation associated with ferroelasticity will contribute significantly to the charge developed (cf. Fig. 6.13). However, the magnitude and duration of the applied force must be such that the changes in polarization due to ferroelasticity are reversible if the output of the igniter is not to deteriorate with usage. 

What is the objection to using PZT compositions of the type developed for piezoelectric applications in a pyroelectric infrared detector What are the properties needed and how have they been achieved ... 

Relaxation Phenomena Hilczer et al. [2002] studied the relaxation behavior of nanoceramic-polymer composites. The smdy focused on a PVDF/PZT composite with 30-nm particles. The dielectric relaxation time of PVDF as well as that of the low-temperature component followed VFTH [Eq. (13.2)]. By contrast, the relaxation time of the high-temperature component obeyed the Arrhenius equation. It is interesting to note that the activation enthalpy increased strongly in composites. The effect was ascribed to the wide-angle oscillation of dipolar groups of PVDF. 

FIGURE 31.21 Dielectric constants and coupling coefficients for PZT compositions near the MPB. 

PZ PT ratio is almost 1 1. At an MPB there is an abrupt change in the structure with composition at a constant temperature. PZT compositions near the MPB have both high k and high k as shown in Figure 31.21. This is where commercial PZT compositions are chosen. 

Figure 18.7 Effective longitudinal piezoelectric coefficient dss and dielectric permittivity 33 for various PZT compositions. The curves are calculated for a single crystal using a phenomenological approach, and shown in comparison with experimental data for a PZTceramic sample. From Ref [36. ...

PZT appUcations (see e.g. Herbert 1982 Mattiat 1971 Rogacheva 1994 Setter and Colla 1993 Uchino 1997,2000 Waanders 1991) cover mainly the field of ultrasonics (ultrasound transducers, cleaners, fluid atomizers, welding etc ), sensors (e.g. for acceleration), gas ignitors, ceramic filters for TV and delay fines, sound transducers for buzzers and also various actuators (e.g. PZT bimorphs, ink-jet printer heads) etc. Although PZT compositions are known for many years they are still excellent for many applications. New PZT modifications are imder development. 

PMMA/PZT Composites (Polar-Polymer/Antiferroelectric Ceramic Systems)... 

As is seen in Figute 34. a plot of a /( ,) represents an experimental relatioa between a, and up to 6 MV/tn. Approximately, relation (18) may also be applied for PMMA/BaTIO, and ndMA/PZT composites containing no more dian 03 vobune bac-tioo of ceramic (Figs. 34 and 35). 

Rguru 44 Oepeadeoce of TW charges oa voiume Cractkm of PZT in FMMA/PZT composite (111). For cooditions, see Figure 43. 

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