Raman Spectra of Strontium Titanate

At room-temperature the Raman spectrum was second-order, in agreement with, the selection rules for the cubic perovskite structure. The second-order spectrum originates largely from pairs of phonons with wave vectors near the Brillouin zone boundary. First-order Raman-active modes predicted in the tetragonal phase of SrTiO₃ are observed on cooling to 120 K, where a new impurity-related band is observed at 793 cm⁻¹. The presence of impurities raised the cubic to tetragonal phase transition temperature to 120 K.