STRUCTURAL CHARACTERIZATION OF GE-S AND GES2-AG2S GLASSY RANGE BY SULFUR K-EDGE X-RAY-ABSORPTION SPECTROSCOPY

EXAFS and XANES S K-edge spectra were collected at room temperature for binary GeS, glasses (1.5 ≤ x ≤ 7) and ternary (1 - y)GeS2 + yAg2S glasses (0.25 ≤ y ≤ 0.50). By EXAFS, only the first coordination shell was resolved. The results, for binary glasses, are consistent with the Chemical Ordered Network model: only S-Ge bonds were found for Ge-enriched glasses (x ≤ 2) while mixed surroundings, constituted by both S-Ge and S-S bonds, exist for S-rich compositions (x > 2). For ternary glasses, only S-Ge bonds have been evidenced. From XANES spectra, it seems that binary S-enriched glasses are constituted by polymeric S chains cross-linked by germanium atoms. On the other hand, for ternary glasses, the XANES spectra show clearly the mixed environment of sulfur with S-Ge and S-Ag bonds. Furthermore, the sulfur surroundings seem rather similar to those of αAg8GeS6 for Ag2S-enriched glasses. © 1993 Academic Press, Inc.