Investigation of (100– x)[0˙5PbO.0˙2B2 O3 .0˙3P2 O5]. x MoO3 glasses
Lead borophosphate glasses of the composition (100–x)[0˙5PbO.0˙2B2 O3 .0˙3P2 O5]. xMoO3 with 0–70 mol% MoO3 were prepared and studied. Thermal studies were carried out with DTA and dilatometry. The glass transition temperature in these glass series decreases steadily with increasing MoO3 content from 467 to 342°C for the range x=0–70 mol% MoO3. The glass structure was studied by 31 P and 11 B MAS NMR and by Raman spectroscopy. These studies were devoted to the investigation of changes in boron coordination and their dependence on the MoO3 content and the B2 O3 /P2 O5 ratio. When the molybdenum oxide and boron oxide content is low, tetrahedral BO4 units prevail in the structural network. With higher B2 O3 content, as well as with higher MoO3 content, trigonal BO3 groups are also formed. 11 B MAS NMR spectra of BO4 units in the glasses with a low boron content reveal two symmetrical signals for BO4 units, ascribed to B(OP)3 O and B(OP)2 O2 units with B–O–P and B (4) –O–B (4) bonds. In the 11 B spectra of glasses with a higher B2 O3 or MoO3 content, the number of B(OP)3 O units decreases, and some B(OP)O3 units appear as well. The formation of mixed BO4 units with B–O–P, B–O–Mo and B–O–B bonds results in several close resonances from which the relative proportion of borate structural units can be obtained. The effect of changing the B2 O3 /P2 O5 ratio on the structure of lead borophosphate glasses modified with MoO3 is also discussed.
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Document Type: Research Article
Publication date: 01 February 2015