New investigations on the LGT crystal intended for time and frequency applications

Materials of the langasite family are of current interest for both Bulk Acoustic Wave and Surface Acoustic Wave devices. In particular, they could be promising solutions to Frequency and Time applications due to their g/product, two to three times higher than for the quartz crystal . We have shown that this encouraging result is strongly linked to the crystal quality and to the post thermal treatment which has been submitted the device. Among the numerous crystals belonging to the LGS family, LGT seems more interesting because of the best combination of quality of growth and material parameters. To qualify the LGT crystal, We have investigated different samples by means Of the infrared spectrometry (IR), the dielectric relaxation spectroscopy (DRS) and the inductively coupled plasma-mass spectrometry (ICP-MS), this last one dealing with the nature and the amount of the chemical impurities. Furthermore, we have investigated the inhomogeneity of our samples coming from different suppliers by measuring their optical rotary power and theIr coefficients Of gyration α at different wavelength.