Piezolectric

Of greater interest in recent years have been the peculiar piezolectric properties"" of polyfvinylidene fluoride). In 1969 it was observed" that stretched film of the polymer heated to 90°C and subsequently cooled to room temperature in a direct current electric field was 3-5 times more piezoelectric than crystalline quartz. It was observed that the piezolectric strain coefficients were higher in the drawn film and in the normal directions than in the direction transverse to the film drawing. 

The piezoelectric phenomena have been used to generate ultrasonic waves up to microwave frequencies using thin polyfvinylidene fluoride) transducers. In the audio range a new type of loudspeaker has been introduced using the transverse piezolectric effect on a mechanically biased membrane. This development has been of considerable interest to telephone engineers and scientists. 

The resonance method is useful when the data are required at only one frequency or at a small number of frequencies. In a typical device used to measure the dynamic tensile storage modulus, the rod, which has a circular or rectangular cross section, is hung by threads at nodal points. An oscillating force is applied at one end of the rod by means of a piezolectric transducer. The response is detected at the other end by a capacitive transducer. To achieve that, it is very convenient to paint the extremities of the rod in front of the transducers with cooloidal silver or another conductive paint. 

Makower, A., Halamek, J., Skladal, P, Kernchen, F., and Scheller, F. W. (2003) New principle of direct real-time monitoring of the interaction of cholinesterase and its inhibitors by piezolectric biosensor. Biosensors Bioelectronics 18,1329-1337... 

In contrast, as noted above, the electrical-ultrasonic efficiency of the piezolectric transducer allows energy to be saved when compared to magnetostrictive transducers. This is probably the main reason why the former is more widely used than the latter, regardless of the relatively low levels of acoustic power intensity provided and the short life-span. Additionally, piezoelectric transducers are high-voltage-driven and air-cooled which, for some applications, implies the risk of explosion (Peshkovsky and Peshovsky, 2010). 

PowCT line insulation. trical appliance ceramic-to- high-tenperature heat-resistant piezolectric... 

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