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Piezoelectric Crystals

March 13th Fact-of-the-Day

Quartz is used almost exclusively to produce frequency-control crystals, because of its satisfactory electro-mechanical properties, low cost, and wide availability. However, natural quartz crystals are almost never found as complete hexagonal prisms with pyramidal ends, so they must be carefully inspected visually with polarized light or in some cases using more elaborate tests to determine whether crystal structures are right- or left-handed and to determine the directions of the axes before they can be properly cut. Electric charges develop on the face of a cut quartz crystal subjected to tension or compression. This is known as the piezoelectric effect. Conversely, a cut quartz crystal contracts or elongates if voltage is applied to it faces. However, care must be exercised when applying voltage to the faces, because extremely small internal energy losses in quartz result in enough mechanical distortion to fracture a crystal with relatively small voltage applied. ©2005 Martek International All rights reserved.


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