Spectroscopy of the O-H and O-D stretching vibrations inSrTiO3under applied electric field and uniaxial stress

High-resolution measurements of the ir stretching bands of OH and OD at about 3500 ${\mathrm{cm}}^{\mathrm{-}1}$ and 2600 ${\mathrm{cm}}^{\mathrm{-}1}$ in monodomain ${\mathrm{SrTiO}}_3$ crystals yield spectroscopic data for a local anharmonic-oscillator model. The optical polarization dependence and the splitting of the absorption bands at low temperature under applied electric field and uniaxial stress give additional evidence for three sets of local oscillators proposed earlier [S. Kapphan, J. Koppitz, and G. Weber, Ferroelectrics 25, 585 (1980)], one being polarized completely perpendicular and the other two forming an angle of 45° with the tetragonal c axis. The main O-H and O-D lines have also been found in Raman spectroscopy displaying the same general behavior and splitting into three components below the structural phase-transition temperature. The above results support the model assuming localized O-H oscillators at regular oxygen lattice sites with the O-H stretching vibration along the oxygen-oxygen directions.