Short-and Intermediate-Range Structural Ordering in Glassy Boron Oxide.
Ordering at short-length scales is a universal feature of the glassy state. Experiments on boron oxide and other materials indicate that ordering on mesoscopic-length scales may also be universal. The high-resolution nuclear magnetic resonance (NMR) measurements of oxygen in boron oxide glass presented here provide evidence for structural units responsible for ordering on short- and intermediate-length scales. At the molecular level, planar BO(3/2) units accounted for the local ordering. Oxygen-17 NMR spectra resolved detailed features of the inclusion of these units in boroxol rings, oxygen bridging two rings, and oxygen shared between two nonring BO(3/2) units. On the basis of these and corroborative boron-11 NMR and scattering results, boron oxide glass consists of domains that are rich or poor in boroxol rings; these domains are proposed to be the structural basis of intermediate-range order in glassy boron oxide.
Youngman
R E
RE
Haubrich
S T
ST
Zwanziger
J W
JW
Janicke
M T
MT
Chmelka
B F
BF