Temperature dependence of Raman spectra of the quartz- and rutile-types of GeO2

 The temperature dependence (at ambient pressure) of the Raman spectra of both the quartz- and rutile-types of GeO2 has been studied from 109 to 874 K. All spectra were corrected for the effects of temperature and are presented in their reduced form to allow a direct comparison of intensities at all temperatures. In the quartz-type GeO2, the Raman bands above 400 cm−1 exhibited relatively larger temperature dependences and at least four of the bands in this region vary nonlinearly with increasing temperature. Deconvolution of the most intense Raman band at 700 cm−1 in the rutile-type GeO2 revealed the presence of a previously unreported band at 684 cm−1 at 298 K which may arise from splitting of the A1g mode. A nonlinear temperature dependence was observed for all the Raman bands above 600 cm−1 in the rutile-type GeO2 with the new band at 684 cm−1 exhibiting the largest curvature. In common with previous studies of rutile-type oxides, the B1g mode at 171 cm−1 showed anomalous behaviour by increasing linearly in frequency with increasing temperature.