Thermal expansion and transition temperature of glasses in the systems BeO–Al2O3–B2O3 and MgO–Al2O3–B2O3

Atomic structure of beryllium boroaluminate glasses: A multi-nuclear NMR spectroscopic study

“…The limited ranges of compositional variation of B and Al speciation and Be coordination environment in the Be-boroaluminate glasses (Table 1) are consistent with the weak compositional dependence of T g and a s for these glasses as reported in a previous study [14]. However, it is also worth noting here that in general glasses with higher BeO:B 2 O 3 ratio are characterized by higher T g values.…”

“…This trend corresponds well with the fact that glasses with higher BeO:B 2 O 3 ratios are also generally characterized by relatively higher concentration of B IV and Al IV species that typically provide increased structural rigidity compared to the B III , Al V and Al VI species (Table 1). The Be-and Mg-boroaluminates are also known to be characterized by the highest a s values among all alkaline-earth boroaluminate glasses [14]. The thermal expansion behavior of a supercooled liquid is expected to be related to the temperature induced changes in the structure and packing of its network which in turn would be related to the configurational entropy.…”

“…Moreover, the extent of such compositional dependence is indeed somewhat suppressed in Mg and Be-boroaluminate glasses in comparison with Ca, Sr and Ba boroaluminates. This situation is especially apparent in the case of Be-boroaluminate glasses which are characterized by the highest T g and a s values and display weak compositional dependence of these properties [14].…”

“…Recent measurements of the compositional dependence of structural thermal expansion coefficient a s and glass transition temperature T g have shown that the variation of these thermophysical properties can be correlated with the short-range structural aspects in a wide range of alkaline-earth boroaluminate glasses [14]. Moreover, the extent of such compositional dependence is indeed somewhat suppressed in Mg and Be-boroaluminate glasses in comparison with Ca, Sr and Ba boroaluminates.…”

Structural role of MgO and PbO in MgO–PbO–B2O3 glasses as revealed by FTIR; a new approach

“…Since MgO increases at the expense of PbO, it is then deduced that the contribution of MgO in modifying the borate network is lower than that of PbO. As known, both PbO [1,2] and MgO [19][20][21][22] can play a dual role in the glassy networks. Under certain conditions, they enter the structure as only network modifiers or both network modifiers and network formers.…”