Piezoelectric materials langasite

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]. 

Other piezoelectric materials require either utilization as single crystal slices cut in fixed relation to the electrical axes, as in a-quartz (Bradaczek et al., 1990) and langasite (Bohm et al., 1999), or as epitaxially deposited layers on suitable substrates (Heywang et al, 2009). 

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