Density and molar volume of extremely modified alkali silicate glasses

The rapid cooling technique has been used to prepare Na 2 O-SiO 2 , Rb 2 O-SiO 2 and Cs 2 O SiO 2 glasses having very high alkali oxide contents. The density and molar volume have been analysed to calculate the volume of the structural units from Q 4 to Q 0 . The changes in density with alkali oxide content reflect the structural changes in the glasses. The structural unit volume increases with increase in the number of nonbridging oxygens. The increase in volume from Q 4 to Q 3 is always lower than the increase accompanying the conversion from Q 3 to Q 2 , Q 1 or Q 0 . The rate of volume change depends on the alkali ion and it increases from Li + to Cs + . Relations are given to calculate the structural unit volume as a function of alkali ion radius.