PZT rod

Gururaja TR, Schultze WA, Cross LE, Newnham RE, Auld BA, Wang YJ (1985a) Piezoelectric composite materials for ultrasonic transducer applications. Part 1 Resonant modes of vibration of PZT Rod-polymer composites. IEEE Trans Sonics Ultrason SU-32 481-498 Gururaja TR, Schultze WA, Cross LE, Newnham RE (1985b) Piezoelectric composite materials for ultrasonic transducer applications. Part II Evaluation of ultrasonic medical applications. IEEE Trans Sonics Ultrason SU-32 499 513... 

The 13 composites are the most examined and applied ones. They consist of individual PZT rods or fibers embedded in a poljuner matrix and oriented parallel to the poling direction. Fiber diameter and spacing, composite thickness, volumetric PZT content, aspect ratio (radius/length) of the fibers and the stiffness of the pol3uner matrix have an influence on the composite performance. The force transfer between the rods or fibers and the pol3rmeric matrix is due to shear-coupling at the poljuner-fiber interface or due to compressive coupling at the front end of the fiber bimdle. 

In PZT rod design [5] the rod shape was chosen to minimize the composite density and lower the dielectric coefficient Sj. by reducing... 

The requirements for medical ultrasonic imaging transducers are met with 1-3 PZT-rod/polymer-matrix piezoelectric composites. The composites provide high electromechanical coupling and low impedance properties superior to those of the conventional piezoceramics and piezopolymers. Also composite plates can be formed into complex shapes for beam focusing and steering. 

These structures were recorded by a vectorial focal spot scanning in a spiral-by-spiral method rather in a raster layer-by-layer mode using a PZT stage. Such spiral structures fabricated in SU-8 have optical spot bands in near-lR [24], telecommunication [25], and 2-5 pm-IR region [26] or can be used as templates for Si infiltration [11]. It is obvious, that direct laser scanning is well suited for defect introduction into 3D PhC, as demonstrated in resin where a missing rod of a logpUe structure resulted in the appearance of a cavity mode in an optical transmission spectriun [27]. 

Fig. 54. a A typical image of closely packed pZT plasmid DNA molecules adsorbed onto a cationic lipid membrane of dipalmitoyldimethyl ammoniumylpropane. The image was recorded in 20 mMNaCl [513]. b Height image of tobacco mosaic viruses on the mica surface modified with bovine serum albumin (BSA). In contrast, direct adsorption from a solution containing BSA led to disperse adsorption of the TMV rods [517]... 

Because of the very large differences in mechanical compliance between the two phases, the hydrostatic pressures experienced by the polymer phase transfer forces to the rods magnifying the stress in them in the poled direction. This magnified stress increases the charge induced on to the electrode tending to compensate for the inactive polymer. As a result, in typical practical cases, the piezoelectric charge coefficient fi/13) is not very sensitive to volume fraction of PZT . 

Experimental Techniques. A block diagram of the experimental set-up used for saturated absorption experiments is shown in Figure 1. The argon laser is a commercial 4W tube in a home made cavity. This cavity is made of three Invar rods, decoupled from the tube in order to avoid vibrations. Line selection is made with a prism, and single frequency operation is obtained with a Michel son interferometer. The laser can be frequency locked to a stable Fabry-Perot resonator with a double servo-loop acting on a fast PZT for line narrowing and on a galvo-plate for wide tuna-bility. This results in a linewidth of less than 10 KHz and a continuous tunability of 6 GHz. 

Concerning the laboratory devices used for sonochemistry, common cleaning baths are constructed aroimd one or more ceramics fitted to the external face of a tank (p. 304). Such devices work at a single frequency, generally between 20-50 kHz, fixed by the manufacturer with an acoustic power of ca, 1 W. Immersion horns are used when more acoustic power is required. Emitters are composed of a "pancake" of PZT ceramics compressed between a titanium rod and a steel countermass (p. 305). Usually horn devices work from 20 to 100 kHz, and the acoustic power emitted can reach several tens of W. For higher frequencies, piezoceramics are simply fixed to the reactor. The reader interested in the construction of ultrasonic devices should consult Ref. 21. 

Shown in Fig. 3.16 is a 1-3 piezoelectric composite with PZT ceramic rods embedded in a polymer resin. This structure is now widely used in medical ultrasonic transducers because the polymer helps reducing the acoustic impedance mismatch between human body and the PZT so that energy transmission becomes more efHcient. The load on the polymer phase can be transferred to the ceramic so that the effective load on the ceramic is enhanced, which produces higher electric signal when it is used as stress sensor. This composite structure also gives a much higher figure of merit for hydrophone applications [18],... 

Safrtfi [86] has made 1 3 piezocompoailes by having different kinds of potymers flooding a Uyer of ceramic balb of PZT. Other 1>3 composilcs aic polymer matrices with ceramic rods placed inside [87]. 

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