Raman scattering in Ti2O3-V2O3alloys

Abstract

Raman scattering of single crystals of ${\left({\mathrm{Ti}}_{1-x}{\mathrm{V}}_x\right)}_2{\mathrm{O}}_3$ with $0\le x\le 0.3$ has been measured between 80 and 700 °K. All seven Raman-active phonons of the $D_{3d}^6$ space-group symmetry were found to show appreciable changes in the frequency, linewidth, and relative intensity as a function of temperature and alloy composition composition in the vicinity of the semiconductor-to-metal transition. In particular, a marked anomaly was observed in the temperature behavior of the lowest frequency mode of $A_{1g}$ symmetry. For $x\lesssim 0.04$ it shows an initial softening followed by a partial recovery in going through the transition temperature. Chi and Sladek have observed a similar decrease and partial recovery for the sound velocity in ${\mathrm{Ti}}_2$ ${\mathrm{O}}_3$. A qualitative discussion of some of these results is given in terms of the free-energy band-crossing model of Zeiger and co-workers.