Abstract
In the field of piezoelectric crystals, quartz is one of the widely used materials in industry for electronicdevice applications as oscillators for the time-frequency domain. α-quartz SiO2 shows a decrease of itspiezoelectric properties above 250°C, an α-quartz to β-quartz phase transition at 573°C and a lowelectromechanical coupling factor of about 8%. Although its nonlinear optics properties are well known, its lowχ(2) coefficient prevent it to be used in frequency doubling devices. The goal of this study is to increase thestructural distortion and the polarizability of this material by substituting part of the silicon atoms with largeratoms such as germanium or other elements. In order to grow centimeter-size single crystals we usehydrothermal methods in high-pressure autoclaves. Crystal growth of mixed α-quartz Si(1-x)GexO2 crystals wassuccessfully performed on pure α-quartz SiO2 (001) seeds. Large crystals with different germanium content wereobtained and analyzed by infrared spectroscopy and EPMA. Piezoelectric and nonlinear optical properties weremeasured on these crystals, which exhibit a improved physical properties. Then, crystal growths with largerelements than germanium were performed in order to further improve their physical properties. Substitution bythe following elements: Mn, V, Ti and Sn were investigated.