The structural response of network former mixing in barium borosilicate glasses: Part 1

Abstract A glass series with constant ∼30 mol% BaO in the BaO–B 2 O 3 –SiO 2 system was studied as a function of SiO 2 /B 2 O 3 ratio. This system has been studied in‐depth to reveal the structure, Part 1, and its relationship to the mechanical properties, Part 2. Both the B coordination and network polymerization are quantified both experimentally, using Raman, IR, and 11 B NMR spectroscopies, and theoretically, using classical molecular dynamics (MD) simulations with effective partial charge potentials with composition dependent boron parameters. These results show that III B, threefold‐coordinated boron, increases linearly with increasing boron, at the expense of IV B. The Q 3 equilibrium constant decreases slightly with boron addition up to 37 mol%, whereas at greater B 2 O 3 contents, the silica tetrahedra become more polymerized. These trends are reinforced by MD simulation results, which show that the average connectivity, polymerization, and ring size are directly related. The glass transition temperature increases with increasing silica content, where the range of temperatures follows the packing density. The BaO–B 2 O 3 –SiO 2 system shows systematic trends from high to low oxygen packing between the binary borate glasses to the binary silicate glasses, indicating a high degree of predictability for properties controlled by density.