Effect of B2O3/P2O5 substitution on the properties and structure of tin boro-phosphate glasses

Effect of B2O3/P2O5 substitution on the properties and structure of the ternary 67SnO-(33-x)P2O5-xB2O3 composition line (from x = 0-33 mol%) are examined in this contribution. We show that density and glass transition temperature increase while molar volume and thermal expansion coefficient decrease with increasing B2O3 concentration. Density and thermal properties experience an original three-domain evolution with rapid (region I: 0 ≤ x < 5), substantial (II: 5 < x ≤ 15), and moderate (III: 15 < x ≤ 33) increase. In order to explain this unconventional behaviour, the glass structure has been investigated using high magnetic field 1 dimensional 31P and 11B MAS-NMR, micro-Raman and infrared spectroscopies. 11B MAS-NMR experiments allow to (i) monitor the 3- and 4-fold coordinated borate species proportion and (ii) highlight the presence of unreported 4-fold coordinated species in the region (III). Finally, it is shown that substitution of P2O5 by B2O3 induces an alteration of the dimeric phosphate network and formation of mixed anion structure that consists of Q0 phosphate units, 3- and 4-fold coordinated borate units and their combinations.