Curie brothers

A few months later, Lippman (1881) predicted the existence of the inverse piezoelectric effect By applying a voltage on the quartz plate, a deformation should be observed. This effect was soon confirmed by the Curie brothers (Curie and Curie, 1882), who designed a clever experiment to measure the tiny displacement, as shown in Fig. 9.2. Here, a light-weight lever with an arm of about 1 100 amplifies the displacement by two orders of magnitude. An optical microscope further amplifies it by two orders of magnitude. The displacement is then measured by an eyepiece with a scale. 

Because strain is a dimensionless quantity, the piezoelectric coefficients have dimensions of meters/volt in SI units. Their values are extremely small. In the literature, the unit 10 mA is commonly used. For applications in STM, a natural unit is A/V, or 10 m/V. Using primitive means as shown in Fig. 9.2, the Curie brothers (Curie and Curie, 1882) obtained a value of 0.021... 

From the very beginning of their experiments, the Curie brothers realized that the linear piezoelectric effect only exists in anisotropic crystals, such as quartz, tourmaline, and Rochelle salt (Curie and Curie, 1880). In fact, as seen from Fig. 9.3, if the +z and -z directions of the plate are equivalent, by reversing the direction of the electric field E-s, the strain should be the same. In such cases, the strain should be proportional to Es 1 instead of E3. In other words, there should be no linear piezoelectric effect. 

Piezoelectricity was discovered by the Curie brothers in 1880. The term piezo is derived from the Greek word meaning "to press." The effect causes a crystal to exhibit electrical polarity when the crystal is subjected to mechanical pressure. Conversely, ihe crystal is physically deformed when subjected to an electrical potential. Specifically, piezoelectricity is a property of nonconducting solids dial have a crystal lattice that does not have a center of symmetry. 

The Curie brothers were drawn to the subject of piezoelectricity because of their familiarity with a phenomenon known for many centuries, that of pyroelectricity. Pyroelectricity refers to the tendency of certain materials to generate an electric current when they are heated. The phenomenon was first described in 314 b.c.e. by the Greek philosopher Theophrastus (ca. 370-ca. 285 b.c.e.), who observed the effect with the mineral tourmaline. Little research was done on pyroelectricity until the early 1800s, when the effect was rediscovered and studied in detail by the Scottish physicist Sir David Brewster (1781-1868). Then in 1878, William Thomson, Lord Kelvin (1824-1907), offered an explanation of the atomic changes that take place when pyroelectric effects occur. These developments in the understanding of pyroelectricity led the Curie brothers to study the possibility of producing electricity from crystals by physical means other than heating. 

The Curie brothers [1] are accredited with being the first to describe the phenomenon of piezoelectricity. However, piezoelectricity remained a scientific curiosity until the war in 1914, when the echo method utilizing piezoelectric plates was developed to explore the ocean bottom. The development of other devices using crystals as control elements followed and eventually the art of crystals became one of the cornerstones of the network of communication systems. 

The phenomenon of piezoelectricity was first discovered by the Curie brothers in 1880 (1). They proposed that when compressed,... 

Piezoelectricity links the fields of electricity and acoustics. Piezoelectric materials are key components in acoustic transducers such as microphones, loudspeakers, transmitters, burglar alarms and submarine detectors. The Curie brothers [7] in 1880 first observed the phenomenon in quartz crystals. Langevin [8] in 1916 first reported the application of piezoelectrics to acoustics. He used piezoelectric quartz crystals in an ultrasonic sending and detection system - a forerunner to present day sonar systems. Subsequently, other materials with piezoelectric properties were discovered. These included the crystal Rochelle salt [9], the ceramics lead barium titanate/zirconate (pzt) and barium titanate [10] and the polymer poly(vinylidene fluoride) [11]. Other polymers such as nylon 11 [12], poly(vinyl chloride) [13] and poly (vinyl fluoride) [14] exhibit piezoelectric behavior, but to a much smaller extent. Strain constants characterize the piezoelectric response. These relate a vector quantity, the electrical field, to a tensor quantity, the mechanical stress (or strain). In this convention, the film orientation direction is denoted by 1, the width by 2 and the thickness by 3. Thus, the piezoelectric strain constant dl3 refers to a polymer film held in the orientation direction with the electrical field applied parallel to the thickness or 3 direction. The requirements for observing piezoelectricity in materials are a non-symmetric unit cell and a net dipole movement in the structure. There are 32-point groups, but only 30 of these have non-symmetric unit cells and are therefore capable of exhibiting piezoelectricity. Further, only 10 out of these twenty point groups exhibit both piezoelectricity and pyroelectricity. The piezoelectric strain constant, d, is related to the piezoelectric stress coefficient, g, by... 

James Clerk Maxwell, a friend and colleague of Professor Thomson s, worked to unite research into electricity and magnetism into a unified, consistent theory of electromagnetism (Maxwell, 1861, 1865), which was also studied by the Curie brothers... 

Piezoelectricity. The Piezoelectric Ejfect. Because all acoustic gravimetric sensors are based on the phenomenon of piezoelectricity, it seems appropriate to discuss briefly the effect itself. Piezoelectricity was first observed by the Curie brothers (Jaques and Pierre) in 1880 [258]. It is a reversible phenomenon, consisting of linear electromechanical interactions between mechanical and electrical properties in certain crystals (Fig. 52). The effect is generated, as already men-... 

The principle of functionality of the EQCM is based on the fact that quartz, like some other materials (tourmaline, topaz, Rochelle salt, langasite, niobate, gallium-orthophosphate), is a piezoelectric material. Piezoelectricity was discovered in 1880 by the Curie brothers, Pierre and Jacques. It did not have the immediately impressive spread and use in the scientific community as other physical phenomena based on high frequency or on electromagnetic fields. However, in the USA, quartz crystal resonators were used in World War 1 in improving the ultrasonic submarine detectors [36]. 

In a review regarding piezoelectricity, Ballato (1996) revealed that Coulomb was the first to suspect that electricity generation could be attained through applying pressure to materials. Katzir (2006) pointed out that Jacques Curie and Pierre Curie were the first to observe piezoelectricity in 1880. It is interesting to note that in 1881, it was not the Curie brothers but Lippmann (1881) who announced the existence of a converse piezoelectric effect. Basically, this converse effect is deformation of a piezoelectric material due to influence of an applied electrical field. Lippmann (1881) postulated the existence of this effect through mathematical prediction by applying basic thermodynamic principles to reversible processes. Curie and Curie (1881) verified and estab-hshed the converse piezoelectric effect experimentally soon after. 

In die late nineteenth century, scientists quickly adopted flie seminal publications of the Curie brothers. Consequently, piezoelectricity and electrostriction were first discovered and investigated on inorganic, mono- or polycrystalline materials (Katzir 2006). Therefore, the theoretical treatment of tire relevant electromechanical properties has been based on the physics and in particular on the structure and the anisotropy of crystals (Newnham 2005 Tichy et al. 2010). Semicrystalline or amorphous polymers are usually less anisotropic flian crystals, and the symmetry... 

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