Temperature dependence of the A₁ and E optical phonons in BaTiO₃

Measurements of all A 1 and E transverse and longitudinal phonons in BaTiO 3 are reported in the temperature range 10 to 132 °C where the crystal is in the tetragonal phase. A least squares fitting of the spectral shapes is done and the resulting temperature dependence of the frequencies, linewidths and coupling parameters is presented. The temperature dependence of the phonon and electron contribution to the dielectric constant, ε, in the c ‐ and α‐axes is determined and compared to the capacitance measurements. It is found that the dielectric constant discrepancy is highly anisotropic.