Studies performed of acoustic loss in langasite, langatate, and langanite.Langasite and its isomorphs, such as langatate and langanite, have attracted significant attention in recent years as materials for improved electronic oscillators An electronic oscillator is an electronic circuit that produces a repetitive electronic signal, often a sine wave or a square wave. A low-frequency oscillator (LFO) is an electronic oscillator that generates an AC waveform between 0.1 Hz and 10 Hz. and filters. The potential advantages of these crystals over quartz include higher piezoelectric The property of certain crystals that causes them to produce voltage when a mechanical pressure is applied to them such as sound vibrations. This technique is used to build crystal microphones, phonograph cartridges and strain gauges, all of which turn mechanical movement into voltage. coupling, which enables devices to be made smaller; lower acceleration sensitivity; and higher Q, which reduces phase noise and enables higher-frequency operation. However, higher Q has been observed only in a few crystals, and acoustic properties usually vary significantly within a single boule boule Deliberative council in the city-states of ancient Greece. It existed in almost all constitutional city-states, especially from the late 6th century BC. In Athens the boule was created as an aristocratic body by Solon in 594 BC; later, under Cleisthenes, 500 members . In order to identify physical mechanisms responsible for degradation of the performance, researchers at NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. have performed a series of studies of the acoustic loss [Q.sup.-1] in langasite, langatate, and langanite as a function of frequency and temperature, using a unique noncontacting acoustic-resonance system. The results show that, in each material, anelastic defect relaxations are the dominant contributions to the loss at all temperatures where measurements were performed (100 K to 750 K). The intrinsic loss (arising from phonon-phonon scattering scattering In physics, the change in direction of motion of a particle because of a collision with another particle. The collision can occur between two charged particles; it need not involve direct physical contact. ) is not apparent in any of the measurements, which suggests that the maximum attainable Q may be significantly greater than values reported thus far. This work was partially supported by a grant from the U.S. Army Research Laboratory. CONTACT: Ward Johnson, (303) 497-5805; wjohnson@boulder.nist.gov. |
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