Abstract
Barium borophosphate glasses of composition BaO⋅2(1-x)B2O3⋅2xP2O5 have been prepared and their constitution of network has been discussed on the basis of composition dependence of the molar volume, elastic constants and Raman spectra which are compared with those of the potassium glasses. The trend of variation of the molar volume and elastic constants for the barium glass is similar to that of the potassium glass: the molar volume increases with increase in x with a plateau near x=0.5 in the volume vs. x curve, at which value of x the elasticity reaches a maximum. This shows apparent similarity in constitution of the barium glasses to the potassium ones. From the log-log plot of bulk modulus vs. mean atom-pair volume for both systems it is concluded that the higher elasticity of the barium glass than the potassium one is due to the stronger interaction of barium cations with their environment. Raman spectra for the barium glasses with smaller x have a band due to boroxol groups, showing elimination of Ba2+ ions from BO4- units accompanying decomposition of borate rings with a BO4- unit. This indicates that the distribution of BaO to B2O3 and P2O5 in proportion to their mixing ratio is not likely to occur in the barium borophosphate glasses and more BaO is distributed to P2O5 than expected from the mixing ratio.
