Langasite

Ssakharov SA, Larionov IM, Medvedev AV (1992) Application of Langasite crystals in monolithic filters operating in shear modes. Proceedings of IEEE frequency control symposium, pp 713-723... 

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]. 

Fig. 6. Single crystals of Langasite (a)-(c) and (d) grown by Cz-method, and by )a-PD technique, respectivery.

Fig. 11. (a) Equivalent series resistance of quartz and langasite single crystals as a function of resonator vibration modes, (b) electromechanical coupling factor of langasite series as a function of piezoelectric constant. 

Mechanism of piezoelectricity of langasite based on the crystal structure... 

Table 6 shows crystallographic data of LGS and NGS including the lattice parameters measured at various pressures. The pressure dependence of lattice parameters (fli and c) and unit cell volume are plotted in Figure 21. Both of lattice parameters along Oi- and c-directions shrunk linearly with an increase of applied pressure. Noteworthy is that the i-axis is preferentially shrunk direction compared to the c-axis. This indicates that the compression of langasite crystals occurs preferentially in the plane. 

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