High Pressure Raman Spectroscopy Study of Α-Quartz-Like Si1-Xgexo2 Solid Solution

Abstract

Spontaneous α-Si1-xGexO2 single crystals were synthesized using the complex of crystal growth techniques: hydrothermal (XGe = 0.09, 0.20), flux (XGe = 0.45, 0.70) and recycling (XGe = 0.96). XRD and spectroscopic studies with non-negative matrix factorization show linear dependences of unit cell parameters and volume and Raman shift on germanium content and confirmed the existence of a complete series of α-Si1-xGexO2 solid solution. The synthesized samples of the solid solution were studied by Raman spectroscopy at the ambient conditions and for the first time at high pressures up to ~30 GPa. The obtained results suggest a phase transition “α-quartz → post-quartz” for α-Si1-xGexO2 in the examined pressure range. The formation of the possible intermediate phase (quartz-II) was detected for α-Si1-xGexO2 with XGe = 0.09, 0.20 and 0.45 at 11, 10 and 7.5 GPa, respectively. The linear dependences of the pressure value of phase transitions on germanium content were observed. At decompression the post-quartz phase remained stable that was determined by Raman spectra for all compositions of solid solution. Obtained experimental results revealed the correlation of the chemical composition, spectroscopic characteristics, and structural deformations at the ambient conditions and at high pressures.

Keywords: oxides (A), crystal growth (B), high pressure (C), Raman spectroscopy (C), piezoelectricity (D)