Abstract : In the field of piezoelectric materials, quartz is still the most used. However its physical properties are too limited for emerging applications. Structure-properties relationships linking either the thermal stability of the α-quartz type phase or the physical properties (dielectric, piezoelectric...) to the structural distortion with respect to the β-quartz structure type have been developed for α-quartz homeotypes. Germanium substitution is believed to be a promising way to improve these properties. Growth of α-quartz type Si1-xGexO2 single crystals was performed by a temperature gradient hydrothermal method in different experimental (nature of the solvent, pressure, temperature) conditions. Crystals were characterized by electron microprobe analysis, high temperature Raman spectroscopy (up to 1100°C) and X-ray diffraction techniques. The structural parameters refinement indicates that the Si-Ge substitution leads to a structural distortion. The α-quartz type phase is stabilized by this distortion. Thus the α ↔β phase transition temperature increases with the amount of Ge atoms and the dynamic disorder is reduced even at high temperature.