Short-and Intermediate-Range Structural Ordering in Glassy Boron Oxide
R. E. Youngman 1,
S. T. Haubrich 1,
J. W. Zwanziger 1,
M. T. Janicke 2, and
B. F. Chmelka 2
1 Department of Chemistry, Indiana University, Bloomington, IN 47405, USA.
2 Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA.
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 BO3/2 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 BO3/2 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.
Submitted on March 6, 1995
Accepted on June 26, 1995
