Chemical order in binary Se-Te glasses: Results from high-resolution 2D 77Se and 125Te MATPASS NMR spectroscopy

Abstract

The structure of binary TexSe100-x (0 ≤ x ≤ 35) glasses is studied using high-resolution two-dimensional magic-angle-turning phase-adjusted spinning sidebands (2D MATPASS) 77Se and 125Te nuclear magnetic resonance (NMR) spectroscopy. The 77Se (125Te) isotropic NMR spectra are consistent with the presence of three different kinds of Se (Te) sites, which correspond to Se–Se (Te)–Se, Te–Se (Te)–Se, and Te–Se (Te)–Te environments. The compositional variation of the relative fractions of the three Se sites indicates that the Se and Te atoms are randomly distributed to form [Se, Te]n copolymer chains. The 77Se and 125Te NMR isotropic chemical shifts for Se and Te atoms in isostructural environments are found to display a linear correlation. The systematic compositional variation of the CSA of Se–Se–Se sites can be related to the appearance of Te atoms as next-nearest neighbors of Se atoms in the [Se, Te]n chains.