Modifier coordination and phosphate glass networks

• Published in: Journal of non-crystalline solids Vol. 274; no. 1; pp. 9 - 16
• Main Authors: Brow, R.K, Click, C.A, Alam, T.M
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 2000; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Disordered solids; Exact sciences and technology; Glasses; Physics; Structure of solids and liquids; crystallography; M107; P147; G188; Network structure; Coordination number; Cesium oxides; Ternary compounds; Composition effect; Binary systems; Glass structure; Phosphate glass; Experimental study; Structural models; Magic angle; NMR; Sublattices; Glass transformations; Chemical bonds; Aluminium oxides
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/S0022-3093(00)00178-2

The addition of up to ∼16 mol% Cs 2O to vitreous P 2O 5 reduces the glass transition temperature ( T g) by 150 K, whereas further additions up to 60 mol% increases T g by ∼20 K. 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra indicate that the phosphate network is progressively depolymerized over the entire range of compositions. The property trend is explained by a transition in the Cs + coordination environment, from isolated Cs-polyhedra below ∼16 mol% Cs 2O to a corner-sharing Cs-polyhedral sub-structure in the glasses with greater Cs 2O contents. This ‘modifier transition’ does not occur in Al phosphate glasses. 27Al MAS NMR spectra indicate that the average Al coordination number decreases with increasing Al 2O 3 content to avoid the formation of Al–O–Al bonds in these binary phosphate glasses.