DocumentCode :
2589755
Title :
Crystal quality of LGT samples: Influence on BAW resonators
Author :
Boy, Jean-Jacques
Author_Institution :
Freq. & Time Dept, FEMTO-ST, Besancon, France
fYear :
2009
fDate :
20-24 April 2009
Firstpage :
166
Lastpage :
170
Abstract :
Materials of the Langasite family are promising to design high quality bulk acoustic waves resonators. But, as for quartz crystal, LGS and LGT "boules" exist with different quality grades (not yet normalized). So, to analyze the quality of a given crystal, we have used the same tools allowing the characterization of the quartz crystal: essentially the IR / visible / UV spectrometry coupled to chemical analyzes of impurities content. These experiments and analyzes are performed on LGS and LGT samples coming from different suppliers (in USA, Russia, Japan or France). After that, LGT crystals have been processed into Y-cut planoconvex resonators working at 10 MHz on its 5th overtone. We have observed that these resonators present better results than those of SC-cut quartz resonators (particularly on their Q.f product). But, unlike quartz crystals, the asymptotic approximation of the analytical model of Tiersten allowing optimizing the geometrical parameters for good energy trapping is not verified. If it is possible, for quartz resonators, to maintain the Q.f product constant in the range [1 MHz, 1 GHz], it is not the same case for LGT ones. Nevertheless, we have obtained LGT resonators, manufactured in a best quality crystal sample, with a Q-factor of about 1.8 million on their 10 MHz 5th overtones, measured at working temperatures for which we do not observed activity dips.
Keywords :
acoustic resonators; bulk acoustic wave devices; crystal resonators; IR spectrometry; LGS; LGT; Langasite family; UV spectrometry; Y-cut planoconvex resonators; asymptotic approximation; bulk acoustic waves resonators; chemical analysis; impurities content; quartz crystal; quartz resonators; visible spectrometry; Acoustic materials; Acoustic waves; Analytical models; Chemical analysis; Crystalline materials; Crystals; Impurities; Performance analysis; Spectroscopy; Temperature measurement;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Frequency Control Symposium, 2009 Joint with the 22nd European Frequency and Time forum. IEEE International
Conference_Location :
Besancon
ISSN :
1075-6787
Print_ISBN :
978-1-4244-3511-1
Electronic_ISBN :
1075-6787
Type :
conf
DOI :
10.1109/FREQ.2009.5168162
Filename :
5168162
Link To Document :
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