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 SrTiO 3 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.