Lattice vibrational modes ofLi2GeO3measured by infrared and Raman techniques

${\mathrm{Li}}_2$Ge${\mathrm{O}}_3$ is an orthorhombic pyroelectric transparent crystal with space group $C_{2v}^{12}\left(Cmc{2}_1\right)$. Scott et al. have shown that it can be grown easily in very large boules by the Czochralski technique. We report and discuss infrared reflectivity and Raman measurements of the lattice vibrational modes along all three polarization directions, and the optic index of refraction. The frequencies of the modes determined from the two techniques are in good agreement with each other except that several more modes are observed by the Raman techniques. The clamped-dielectric-constant values calculated from the modes are in fair agreement with our capacitance measurements.