Observation of Satellite Reflections in the Intermediate Phase of Quartz

The intermediate phase (IP) between α and β phases of quartz, which has been reported previously by the present authors, was studied by a fine-beam X-ray Laue method. Then, one could find satellite reflections. The analysis shows that IP has a sinusoidal and displacive modulated structure which is characterized by 6 wave vectors q perpendicular to the a axes. The wave is transversal in the C-plane. The period \({=}q⁻¹\) of the modulation and the associated intensities increase as temperature decreases; i.e. \({=}172{±}10\) Å on β side and 565±25 Å on α side. The satellites are likely owing to the optical mode of the displacive vibration of SiO 4 tetrahedra.