Effect of B2O3 addition on the thermal properties and structure of bulk and powdered barium phosphate glasses

The glass transition temperature increases and the thermal expansion coefficient and density decrease with increasing B2O3 concentration in a series of (100-x)(50BaO-50P(2)O(5))-xB(2)O(3) where x = 0-10 mol% for bulk samples. According to Raman spectroscopy, the bulk BaO-P2O5-B2O3 (BaP-B) glasses consist of metaphosphate Q(2) units with ring-type metaborate, diborate, and PO4-BO4 groups. X-ray photoelectron spectroscopy results reveal qualitatively that P-O-B bonds are formed at the surface of BaP-B glass samples ground in laboratory air over 6 mol% B2O3 only. The P-O-B bonds are related to the suppression of the crystallization of powdered BaP-B glasses with > 6 mol% B2O3 during differential thermal analysis.