Abstract
The spontaneous nucleation by the high temperature flux method of GeO2 and SiO2-substituted GeO2 (Ge1-xSixO2) compounds was improved to give single-crystals free of hydroxyl groups. The crystal structure and quality of these α-quartz-like piezoelectric materials was studied by single-crystal X-Ray Diffraction (XRD) at room temperature. The refinements gave excellent final reliability factors which are an indication of single-crystals with a low level of defects. A good correlation was found between the silicon content in Ge1-xSixO2 crystals determined through extrapolation from the inter-tetrahedral bridging angle and that found from Energy Dispersive X-ray spectroscopy (EDX). The effect of the germanium substitution by silicon on the distortion of the α-quartz-type GeO2 structure was followed by the evolution of both the intra-tetrahedral angle and the other structural parameters. The TO4 (T= Si, Ge) distortion was found to be larger in α-GeO2 than in α-SiO2 and, as expected, the irregularity of the TO4 tetrahedra decreased linearly as the substitution of Ge by Si increased.