RAMAN-SPECTRA AND STRUCTURE OF GAMMA-LN(2)S(3) VACANCY CRYSTALS

Polarized Raman spectra were recorded for oriented gamma-La2S3 crystal s; unpolarized spectra were obtained for gamma-Ce2S3, for (La-Ce)(2)S- 3 solid solutions, and for XLn(2)S(4) compounds (X is metal). The obse rved crystalline modes are assigned according to symmetry types. It wa s found that vacancies are distributed in the cation sublattice statis tically; conditions for ordering of metal atoms are examined. La2S3 sh ows resonance scattering at lambda = 647.09 nm; this is likely to be d ue to disorder in the crystal lattice.