The Relations of Thermal Expansion, Composition and Structure of Glasses. I. The Sodium Oxide–Silica Glasses

JSGT 1951 V35 T304-T317

Previous methods for calculating thermal expansion coefficients from glass compositions have been based on the arithmetic determination of constants from available data to fit assumed additive equations. The proposed new equation for this purpose is derived from constitutional considerations based on the volume of glass containing one gram atom of oxygen. Comparisons are made of the results obtained by using this method with those of several favoured previous methods to demonstrate its marked advantages. The structural implications of the results are discussed. Explanations of the breaks in the physical property–composition curves are advanced with emphasis on the fact that the nonbridging oxygen ions (those not shared by two silicon ions) tend to assume positions in the network as remote from one another as possible or to repel one another at least within the scope of certain short range distances. The relations of this hypothetical mechanism to properties and as an explanation of the variations of properties with thermal histories of glasses are discussed.

Henry H. Blau