Raman studies in tetragonal structure PbTeO₃

Raman spectra of tetragonal phase PbTeO₃ have been acquired from single-crystal sample synthesized by hydrothermal method. Theory calculations have been carried out to analyze the Raman spectra. Raman bands between 600 cm⁻¹ and 800 cm⁻¹ are attributed to the internal modes of Te-O bonds in TeO₃ pyramid, while Raman bands between 136 cm⁻¹ and 400 cm⁻¹ are assigned to the external modes of TeO₃ pyramid. The vibration corresponding to Raman frequencies below 119 cm⁻¹ are consisted of Pb lattice modes and external modes of TeO₃. The effects of pressure on the Raman spectrum of PbTeO₃ have been investigated up to 23 GPa. A splitting of 119 cm⁻¹ peak was observed at 13.4 GPa, which may caused by the rotation of TeO₃ pyramid instead of the phase transition.