Author/Authors :
Petzelt، نويسنده , , J. and Gregora، نويسنده , , I. and Rychetsk?، نويسنده , , I. and Ostapchuk، نويسنده , , T. and Kamba، نويسنده , , S. and Van?k، نويسنده , , P. and Yuzyuk، نويسنده , , Y. and Almeida، نويسنده , , A. and Chavez، نويسنده , , M.R. and Gorshunov، نويسنده , , B. and Dressel، نويسنده , , M. and Hoffmann-Eifert، نويسنده , , S. and Waser، نويسنده , , R.، نويسنده ,
Abstract :
Raman and infra-red spectroscopic investigations of nominally pure SrTiO3 ceramics have revealed a clear presence of polar phase whose manifestation steeply increases on cooling from room temperature. The Raman strengths of the Raman-forbidden infra-red modes are proportional to ωTO1−α (α ≈ 1.5) where ωTO1 is the polar soft mode frequency. Our explanation is based on an assumption of a temperature independent polarization Pf fixed at grain boundaries. The effective polar soft mode is slightly shifted upwards at low temperatures, becomes broader and strongly coupled with the Eg component of the structural soft mode which shows that Pf is perpendicular to the tetragonal c-axis.
Keywords :
Strontium titanate (STO) ceramics , Dielectric Permittivity , Grain boundaries , Polar soft mode
