AMORPHOUS STRUCTURE IN TE-X-I (X-S, SE) MIXTURES

X-ray diffraction and Raman scattering measurements have been carried out on amorphous-(Te3I2)I1-xSx and (Te1/2I1/2)(1-y)Se-y mixtures. The results are summarized as follows. (1) S atoms in the amorphous Te-S-I mixture do not combine with Te and I atoms but form twofold sulfur cl usters, whereas Se atoms in the amorphous Te-Se-I mixture are covalent ly bonded to Te atoms, and form -Se-Te- linkages. (2) 1 atoms are pref erentially bonded to Te atoms in both amorphous mixtures. (3) The coor dination number of constituent atoms in the mixture is determined to b e two for S, Se and Te, and one for I, by a least-squares fit to the o bserved intensity function. (4) The structural feature in the sulfide mixture is substantially unchanged in both amorphous and liquid states , except for an increase in the coordination number around a central T e atom.