ホウリン酸塩ガラスの網目構造(第3報) : バリウムホウリン酸塩ガラスの構成(構造)(<特集>ガラス・アモルファス材料及びその材料科学の進展)

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Barium borophosphate glasses of composition BaO・2(1-x)B_2O_3・2xP_2O_5 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 Ba^<2+> ions from BO_4- units accompanying decomposition of borate rings with a BO_4- unit. This indicates that the distribution ofBaO to B_2O_3 and P_2O_5 in proportion to their mixing ratio is not likely to occur in the barium borophosphate glasses and more BaO is distributed to P_2O_5 than expected from the mixing ratio.
1989-03-01