Study of Inelastic Light Scattering in LaxSr(1-1.5x)TiO3

In an attempt to gain a better understanding of the lattice dynamics in lanthanum doped SrTiO3 (STO) ceramics, with general formulae LaxSr(1-1.5x)TiO3, We have carried out a detailed Raman study of the x=0.0133 ceramic in the temperatures ranging from 10K to room temperature. Our results show that lanthanum substitution gives rise to new features in the Raman spectra. The Rayleigh band and the extra Raman-forbidden infrared active modes observed provide evidence for the existence of disorder in the system, apparently associated with grain structure, and lattice defects. Moreover, the absence of a TO1 polar soft mode supports the non-existence of a ferroelectric phase at low temperatures. The shift of the para-antiferrodistorsive transition temperature towards higher temperatures clearly evidences that the replacement of Strontium by Lanthanum occurs at the lattice A-site.