Raman study of α-quartz-type Ge1−xSixO2 (0 < x ≤ 0.067) single crystals for piezoelectric applications

As potential candidates for high temperature piezoelectric materials, α-quartz-type Ge 1− x Si x O 2 (0 < x ≤ 0.067) single crystals grown by the flux method were structurally and thermally characterized. When compared to pure α-GeO 2 , room temperature polarized Raman spectra contained additional lines which have been assigned from density functional theory on a α-Ge 0.833 Si 0.167 O 2 solid solution. The results highlight that Si-O-Ge bridges were involved. Moreover, a linear relationship between the wavenumber position of the main A 1 Raman lines and the SiO 2 substitution rate x was also observed. The analysis of the temperature dependence of unpolarized Raman signals of an α-Ge 1− x Si x O 2 phase with x = 0.067 pointed out the high-thermal stability up to 1000 °C of the α-quartz-like structure related to the lack of a libration mode and to the absence of a softening mode with temperature. Raman lines due to Ge-O-Si bridges in α-Ge 1− x Si x O 2 single crystals are identified with the help of polarized Raman and calculations.