Ir reflectance spectra ofTi2O3: Infrared-active phonons and Ti3delectronic effects

Abstract

The room-temperature reflectance of ${\mathrm{Ti}}_{2}$${\mathrm{O}}_{3}$ has been measured between 50 and 4000 ${\mathrm{cm}}^{\ensuremath{-}1}$ for the two principal polarizations, $E$ perpendicular and $E$ parallel to the $c$ axis. An analysis of the data provides (i) the properties of the ir-active long-wavelength phonons---TO- and LO-phonon frequencies, oscillator strengths, and the damping; (ii) the values for the optical frequency ${\ensuremath{\epsilon}}_{\ensuremath{\infty}}$ and quasistatic ${\ensuremath{\epsilon}}_{0}$ dielectric constants, and (iii) information about electronic effects associated with the partially occupied Ti $3d$ states. The latter include the anisotropy in the free-carrier electronic conductivity $\frac{{\ensuremath{\sigma}}_{\ensuremath{\perp}}}{{\ensuremath{\sigma}}_{\ensuremath{\parallel}}}$ and the energy separation between the lowest-lying $d$ levels. Comparisons are made with the phonon properties of other $\ensuremath{\alpha}$-corundum structured sesquioxides $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{Cr}}_{2}$${\mathrm{O}}_{3}$.