Heat capacities and thermal behavior of alkali borate glasses

Structural investigations of sodium diborate glasses containing PbO, Bi2O3 and TeO2: Elastic property measurements and spectroscopic studies

“…We speculate that this is a reflection of gradual decrease in liquidus temperatures (not measured in our work) as a consequence of near ideal nature of mixing; T g values (T g = 2/3T liquidus ) decrease continuously. Extrapolation towards y = 0 of the T g line of NBT glasses yields a T g value of 730 K for sodium diborate glass which is in good agreement with literature values (741 K) [62]. In the slightly interacting DB-Bi 2 O 3 system, [BiO 3/2 ] 0 becomes ½BiO 3=2 O n 3 0 in the glasses.…”

Quench rate and temperature effects on boron coordination in aluminoborosilicate melts

“…The BO 3 ring peaks that were assigned in the NMR study are thus more likely to be "modified" ring structures. In the studies of glasses with different cooling rates, no temperature effect was observed for the [3] B sites or between the [3] B and [4] B species in this 30 mol% Na 2 O composition [2,7]. In this paper we present high-resolution NMR data on fictive temperature effects on the structures (primarily boron coordinations) of a carefully designed series of aluminoborosilicate glasses.…”

“…In boron-containing glasses, the exchange between the two coordination numbers has often been related to thermodynamic property changes, e.g. viscosity, melting points, and glass transition temperatures [1][2][3][4][5][6]. Temperature effect studies of some borosilicates suggested that boron network speciation changes probably are a major contribution to the configurational heat capacity [7,8], and thus have large effects on the overall free energies and enthalpies, as well as the shape of the viscosity vs. T curve.…”

“…The high temperature NMR is still experimentally challenging compared with ambient temperature methods. Large uncertainties can also be caused by the difficulty of the deconvolution of three-and four-coordination boron structures from Raman spectra and neutron diffraction experiments: for example, ΔH for reaction (3) was estimated as 60± 20 kJ mol −1 in Raman study for borate melt (Na 2 O) 0.33 (B 2 O 3 ) 0.67 [29], but is 22±10 kJ mol −1 from a neutron diffraction study for a very similar composition (Na 2 O) 0.358 (B 2 O 3 ) 0.642 [31]. Alternatively, we can investigate glass samples prepared by cooling melts at varying rates as structural analogs for melts over relatively limited temperature ranges.…”

Composition and temperature dependence of cesium-borate glasses by molecular dynamics

“…9 This trend is consistent with the alkali dependence of other physical properties, [10][11][12][13][14] including sound velocities and elastic constants which decrease systematically as the alkali changes from Li to Cs. 15 Such a disagreement for the role of metal ions, resulted from parallel studies of the structure and properties of alkali borate glasses, appeared to be resolved in more recent NMR investigations of Zhong and Bray 16 and Bray. 17 By employing wide-line 11 B NMR with more sensitive instrumentation and signal-averaging techniques, they were able to demonstrate that N 4 follows the theoretical curve x /1−x for alkali contents lower than ca.…”