title: Tellurium speciation, connectivity, and chemical order in As(x)Te(100-x) glasses: results from two-dimensional 125Te NMR spectroscopy.
abstract: The short-range structure, connectivity, and chemical order in As(x)Te(100-x) (25 ≤ x ≤ 65) glasses are studied using high-resolution two-dimensional projection magic-angle-turning (pjMAT) (125)Te nuclear magnetic resonance (NMR) spectroscopy. The (125)Te pjMAT NMR results indicate that the coordination of Te atoms obeys the 8-N coordination rule over the entire composition range. However, in strong contrast with the analogous glass-forming As-S and As-Se chalcogenides, significant violation of chemical order is observed in As-Te glasses over the entire composition range in the form of homopolar As-As (Te-Te) bonds, even in severely As (Te)-deficient glasses. The speciation of the Te coordination environments can be explained with the dissociation reaction model As2Te3 → 2As + 3Te(II), characterized by a dissociation constant that is independent of glass composition. These structural characteristics can be attributed to the high metallicity of Te and the strong energetic similarity between the Te-Te, Te-As, and As-As bonds, and they are consistent with the monotonic and often nearly linear variation of physical properties observed in telluride glasses as a function of the Te content.
authors.affiliation: Division of Materials Science, University of California at Davis , Davis, California 95616, United States.
authors.forename: Derrick C
authors.initials: DC
authors.lastname: Kaseman
authors.forename: Ivan
authors.initials: I
authors.lastname: Hung
authors.forename: Kathleen
authors.initials: K
authors.lastname: Lee
authors.forename: Kirill
authors.initials: K
authors.lastname: Kovnir
authors.forename: Zhehong
authors.initials: Z
authors.lastname: Gan
authors.forename: Bruce
authors.initials: B
authors.lastname: Aitken
authors.forename: Sabyasachi
authors.initials: S
authors.lastname: Sen